The guy I just sold my SV to. I spent a good 3 hrs walking him through the carbs & fueling, how to disassemble the fuel system & where everything was, why? because I knew & he wanted to know. as bikers its our duty to pass on info to those willing to try. great vid man.
especially since once all the electronic fuel injected bikes have fallen apart, the old bikes will still be running in the mad max like dystopian future.
Fantastic explanations. Appreciate how you explained things more in layman’s terms. I’m one of those guys that I’m still learning mikuni flat slide bst 36s. Been a challenge. Still trying to fine tuning. The fuel air jets at 1.5 turns out. Thank you
At last, someone who doesn’t refer to the whole world as ‘guys’ and isn’t wearing a baseball cap backwards. Thanks for the intuitive explanation of how to tune carbs. Much appreciated.
I don’t think any video I’ve watched on carburetors has ever told me anything I didn’t know or was any help to except this one this guy is awesome thank you for this video
Many many tears ago I worked in a large bike shop in Sydney, I had many many young blokes come in to buy a power band. The first was quite funny but after that we had a little spiel to help them understand what it was, what a reed valve was and how jets and cutaways worked. Most of those guys were dirt bike guys with two strokes and I think they mixed up the new reed valve technology with discussions about power and performance etc. yes, it our job to help our fellow riders understand and learn. After all it really is true that every day is a school day.
Just used a 4 dial vac gauge on my XJR1200, lots of fiddling around, the workshop book never mentioned a master port to work off of, just said to sync them all the same with idle set or adjusted after each change was made. I came to the conclusion it ran pretty much the same but tick over was a bit smoother. Lovely bike you have there btw!
excuse my language but this video is fucking awesome, haven't finished it yet but i had to stop and write the comment. I'm not a novice with carburetors or engines but i know how to do stuff, not necessarily why things act or work the way they do. It's good to find videos that show why problems happen and why solutions work not just instructional videos and how to
I tried making a homemade synchronizer with a plastic bottle and clear plastic tubing with auto trans fluid. Didn't know how much vacuum the Mikuni's pulled so it didn't work. (Yes, I shut the engine off after seeing the fluid about to go into the carbs.) Bought a 4 gauge sync at a local bike shop for $60 and it's one of the best investments I've made. Time to work on the wife to get me a colortune!
Great video. I think the confusing part for some folks is the terminology. I use the term 'balance' to describe the gas to air mix for each carb and 'synchronize' as the term to describe adjusting the carb butterflies to be the same.
Hi Andy, my second name is the same, & some friends only know me by that name. I have been following & really enjoying your posts, especially those of the XS 11. I have a 79 XS 11 F, bought as new. It has done 46 thousand kilos, but has been standing 12 years now, due to it having caught alight in 2006, minimal damage though. I had added carburettor cleaned to the fuel, & unfortunately there was a minute rust hole held closed by the paint all the years, which was opened by the carb cleaner, which allowed the fuel to spray onto the plugs, hence the fire. Unfortunately I left the fuel in the carbs for too long, & as a result minute holes were eaten into of the brass floats, & the carbs were a mess when I eventually opened them up! I found Acetic acid cleans the brass very well but doesn't eat any metal, even the aluminium. I retired at 65 last year, so now have time to do some minimal "rebuilding" of my bike to get it back on the road. Fortunately I'm still very much on my feet, young at heart, & able to still enjoy my bike when it'll be back back on the road. Its still in a very good condition. Just one question ... What would be your opinion regarding its bores? Do you think I need to open it up to check on rust? I I've in Port Elizabeth South Africa, maybe a climate similar to you side?? The bike has always been well covered in the garage, the inlet ports stuffed with rags. I do maybe have to replace the valve guide seals, as it used to burn an oily sediment on the exhaust end, but that I could see, it didn't smoke. Maybe I should just open it anyway, replace the oil seals, although I'm keen to ride the bike. I do remember that if it stood long, it would smoke after standing, but once warmed up would stop smoking once warm and started a second time, so probably valve guide seals? Not sure if you're still posting, as Uve only recently discovered your posts and enjoy them, they're interesting & informative, just great! Go well!
@@jerryking1434 Hi. Unfortunately I'm not anywhere near that yet. I'm a member of the Triumph Sports Car Club, Port Elizabeth, the name now been changed by this idiotic government to some other unpronounceable name, here in South Africa. I've been working on a club member's cars, the last of which I hope to give back to the guy by the end of next week. Only then am I going to be able to look ahead at my very patient bike that I'm dying to get back onto! In the meantime I've progressively prepared and planned ahead and should have everything ready to start immediately once my other commitments are cleared. Its been a long wait!
We moved to a higher elevation.. from 1000 ft So Cal to 4600 ft Arizona ... runs kind of ragged.. My issue is I have both fuel and air pilot screws. Mikuni VM28SS on '79 Suzuki GS1000EN.. I'll keep working on it until it's right, but your video simplifies the process very well. any general tips? I really don't want to re-jet if I can get by without. None of the bike shops around here work on these old carb bikes.. at least for tuning... thanks..
Another great video Andy, i have mounted the Brembo conversion on my xs1100 since i last commented. Turned out to fit absolutely perfect. No caliper clearance issues at all and mounted up to the forks easily with the supplied bracket. Now i need to run my brake lines and finish that up. The wiring on the bike is still a nightmare
If you are using aftermarket levers you may not be getting the mechanical advantage you need (the XS11 clutch lever is very long). If you have heavy duty springs in your clutch you can try replacing two, diagonally opposite, with standard springs. Other than that all I could suggest is clean and lube everything, including your cable, and make sure that the cable isn't being impeded anywhere. Maybe some time in the gym lol.
Thanks for the speedy reply i love watching your videos. i got some used carbs on ebay which were surprisingly clean and look like they're in way better shape than the ones my bike originally had. the wiring is still a bit of an octopus. Wiring it with the motogadget m-unit is proving to be harder than i thought. i got the starter to work by running wire to the switch but thats about it!
I have a 1981 Yamaha xj750 and rebuilt the carburetors, but now it runs worse, doesn’t even want to idle and when I hit the gas, it drops down and then revs up. Do you think it needs to be synced?
I’ve been having issues with either fuel or air getting through. My tanks dirty but I’ve cleaned it and also cleaned the carbs (carbs have always looked fairly well inside no clogs at all just some settlement at the bottom) however the bike surges at idle and while riding. When you choke it it sets at 2000 rpm am slowly he’s up to 3-4 and then drops back to 1. If I play with fuel mixture screw it’ll stay running at the cost of hanging revs. I just had it tuned not long ago but it already sounds like crap again
Hi Andy ! As i promised, i came with my questions. I think it will be more easy for you if i just leave what i have done, changed on bike and my current problems, so you can have a diagnosys of your own. Because, obviously besides you, my mechanical skills and knowledge cry outs :D It was a 22 year old GN 250 working fairly good. (Had some prolems on carb) I'm skipping visiual changes, focusing on mechanical ones So; 1. As soon as i bought it, i have done a top end rebuild with 300 cc BBK. Replaced clutch plates, valves, starter motor, rectifier, air filter, all fluids and tyres etc.. 2. It worked pretty well (it still works), i achieved my goal which was increasing the torque of it. And i replaced the sprocket combination from 15/41 to 15/38. Also changed the slip on with a new one which is almost same as the old one in back pressure manner, but of course looking better... 3. After a 500 km running in breaking process, i gave it a full throttle to see the top speed. It was about 110km/h on 5th gear. I was pretty unhappy about it because original set up could do 130 in good condition. I have observed it very carefully and saw that it won't go above 6.500 rpm. 4. So i decided to change the main jet as usual and did it from #130 to #135 and pilot jet from #40 to #42.5 ( i had lots of bogs at mid rpm. with that change it all gone and now it's bumber and smooth at mid rpm/throttle position) It didn't matter so much. It just ran smoother. Also, replaced the spark plug with the same numbered iridium one. No improvments. 5. Then i took of the air filter from the box, boom, the torque was raised by God's hand, but still no improvment at high rpm on 4th and 5th gears. It just won't go above 6.500, even getting there so hard. Btw, there is no problem on 1th, 2th and 3th gears. I see 8.500-600 rpm which is the enter into red line for GN250s. I checked the diaphram and slide on carb and there was no prob. But still to be sure, i got a new one. I didn't put it yet. Also i bought an Apexi air filter that is waiting for putting. It starts at first attempt in cold wheater. Just won't go above 6.500. Even it arrives there pretty hard. Maybe it will go above 6.500 like 7.000 but down the hill. Thank you in advance...
Hi Ali, I will sit down, read and digest this when I did some time to focus on it. We are heading interstate this week and are doing the family Christmas thing this weekend with the grandkids etc. I promise I’ll get back to you soon, Andy
Andy's Motorcycle Obsessions Don't worry Andy, I have time and in mean time I will let you know about the upgrades that I'm going to do soon. Thank you a lot, I have already learned a lot from you. Waiting for your wise advices ! Cheers ! (BTW, I'm from Turkey and if you need anything related to my country, I'd be happy to help. Just letting you know) Have a nice day, I'm going to sleep now :D
Id like to try one of those Colortune plugs, but cylinder 2 and 3 are a pain in the ass to get to on my 1975 CB750. Seems like it would be hard to check those two, even with that mirror tube thing it comes with. I could do 1 and 4 easily. I have a Morgan Carbtume Pro for my syncing, which works well. I'd like to try the DigiTec out at some point.
I've got rs34's on my cb 750 and they are a total nightmare to balance, even when you did your correct adjustment and go to lock it down with the locking screw the adjusted is knocked out
I hate carburetors after having a fuel injection. I just sold my last of many motorcycles with carburetors. Now all my motorcycles have fuel injection..I won’t miss vacuum diaphragms, nozzles, needles, needle clips, needle and seat, floats, pilot jets, air screws, atomizers, enriching circuits, chokes, main jets, ticklers,.. I remember trying to synchronize for carburetors on the 1969 Honda CB 750 with vacuum gauges. Each carburetor had its own cable. You could get all the carburetors close to balanced, then blip the throttle one time, and they would be all screwed up..I remember having to jet my route race machines for racing at mid Ohio, then having to go fat for daytona jetting at sea level.. You had to carry Jets to change for elevation went dirtbike riding in the Rocky Mountains . you had to pull over and put in a leaner main jet the higher you went in the mountains. then there were the Suzukis of the 1980s. You simply could not get those machines to run correctly with the EPA doing the jetting for them. many of them were so lean, they would actually slow down if you shifted into sixth gear wide open. They would go faster in fifth gear with the choke partially on..And that was at 1400 feet of elevation. I can’t imagine how poorly they ran at sea level.. I will not miss carburetors ..
Andy's Motorcycle Obsessions of course, CV carburetors do compensate somewhat for altitude. But, none of my dirtbike‘s had CV carburetors. Not my YZ 125, RM 125, CR 125, CT1, CT2 IT 175, IT200, KD 125, KDX 175, KDX 200,(Air cooled), KDX 200, water cooled, DR 100, YT 175,Gas gas jtr250,fantic section 250,BETA jtr 250, XR 250 R, XL 250,tt500... none of my above motorcycles that I have owned from time to time since 1968 have had CV carburetors..And these are just the off-road dirt/trials bikes that I have owned. for street & RR track,into the RDs, cb750,cb400f,z1,DS7,R5,RZ350,H1,S2,A1,A7,350GTR,TZ250D (with lectrons)TD1,td2b,H1-R(yes a sand cast case dry clutch factory Kawasaki H1R-eric buell ended up with the chasis) None of these machines had CV carburetors either I have owned every one of the above machines.. these are just most of the ones I can remember without CV carburetors..They really make me appreciate my fuel injected machines, my current street bikes are a Moto Guzzi Norge, and a Honda GL 1800 .. when I was a Honda motorcycle mechanic at a busy dealership that had seven full-time mechanics. I remember that I bought my current snap on 24 inch number two Phillips screwdriver, just for pulling the carburetors on CB 750s..I remember what a pain in the ass it was to sinc The first generation CB 750 carbs when they each had a single separate throttle cable before bell cranks.. no I do not miss carburetors one bit.. I actually had one 1982 Suzuki DR 100 4-stroke, My wife’s trail bike, a California model. I could never get that motorcycle to carburate correctly.. it wouldn’t run unless you left the enriching circuit on for three or four minutes and let the motor rev without touching the throttle for the first five minutes. Then once it warmed up, trail riding, climbing a steep hill, it would pull, until you went to three-quarter throttle, from 3/4 to wide open, it fell on its face/lean. Let off the throttle, it would start pulling again. I tried needle shims, I tried main jets, I tried , everything I could think of, that California turned by the EP a carburetor could not be made to run correctly. It was not the float setting,, It was not an air leak, it was not low compression, it was not a tight valve. It just went Lucas
Hi, I have both a Intruder VS1400 and Marauder vz800,,,I have the bikes running well and synced,,,However the idle on both of these bikes is a bit off,,,AND upon bliping or reving the throttle on both bikes the idle hangs for a sec before returning to steady idle,,,from my under standing when this happens its typically a lean condition, conversely when you blip a throttle and it dips, then returns to idle its a rich condition,,,,,,,IS this issue solved by simply finding the correct mixture screw seting on both carbs? IF not do you have any other ideas for me to try? TY you have a great channel
I've got some of same stickers; ngk k&n, an I member my brother jokingly try to convince his friend to balance his carb! Haha! While they were raddle can spray painting his 51 chevy an Orange color.
Hiya, I have a 1987 CBR 600F1 that I rebuilt the carbs in. I had a heck of a time getting them adjusted to what seems right. The float heights were difficult to set only due to being confused about the seating position as the Clymer manual was pretty vague. The bike seems to work fine, but I can't tell if its warming up properly or not. I want to say it IS, as the manual states that it takes about 10 minutes of stop-and-go riding to warm the engine up properly, but I can't be so sure as I have no good reference point. I don't like to hop on it early unless I keep the enricher partially engaged as the bike is very easy to stall otherwise but only takes a few minutes of riding until I can turn it off safely. The bike doesn't overheat and it runs at normal temps while idling (3/4 temp gauge) and while riding (1/2 temp gauge or lower.) My other bikes (2007 ex500, 2000 sv650) warm up to riding temps pretty quickly in comparison. Another issue I am having is I have a very very slight stutter at about 1-5% throttle and only if I turn the throttle slightly, but quickly. Almost as if there is a very small delay. Any more than a quarter of a second and the bike revs up just fine. Is this potentially a rich condition at that point of throttle? I've heard of someone else solving by using a slightly larger jet (on a different bike,) but I can't be sure that my issue is as severe as theirs. Finally I have one more issue . . . if I perform a hard stop my rpms will drop and the bike will stall. It immediately starts back up. I figured this was just the fuel rushing to one side of the carbs due to the nature of hard stops, but should this be a problem on this bike? Some others have agreed with me, but this is the only bike I have that exhibits this symptom :/. FWIW - stock jet sizes. Illinois weather (riding in 18-60 degree weather) and parts unlimited brand rebuild kit. Float adjustments were done using a high quality metal ruler and digital caliper after finding other tools to be less accurate. Adjustment screws on each carb were set at manufacturer recommendations. I installed a Jet kit in my sv650 and synced the carbs prior and it runs like a top.
Have you considered that your ignition timing or advance my not be correct? Many of your symptoms could indicate this. There is an old bike mechanics saying, "90% of carburetor problems are electrical". It might be worth looking into.
Thank you! Unfortunately I am not experienced with engine internals, but when its warmer I will flip through my service manual and see what I come up with. My eventual goal with the CBR is to get a 1990 model in OEM paint and install all of the factory pro upgrades - jet kit, ignition advance, etc. to make it as good as can be. Thanks again!
Luckily, here in the UK at the moment we have E10 or E5 petrol, (10%) or (5%) Ethanol, because my bike is 2004 I remove the Ethanol anyway and add an additive to boost the octane back to what it was originally.
Hey, thanks so much! I've got a question: I've seen a video of a guy who disconnects the spark plug from one side of a v-twin, in order to set each carb individually. In my mind that makes sense, since you eliminate any influence by the other carb. However in most videos I've seen by professionals, they let both carbs run. Is there a reason for this, and are there any risks involved with setting one at a time? I'd much appreciate some wisdom on this.
Hello Andy,great videos. They are extremely helpful. I have a gs1000l and am having problems with #3 carb. I followed your videos cleaned and put new kits in them. The engine ran decent but no matter how much I adjusted #3 nothing changed. I took Temps on all exhaust pipes and found #3 was twice that of 1,2,and 4. Meaning a leaking condition. So I'm thinking #3 carb is plugged somewhere. I was wondering what your thoughts on this problem is,could really use your input. Thanks
Alright Andy! I need some assistance....looking for carb/jetting advice to get my twin running right before I roll it off a cliff! 😂 250 V twin Yamaha, running straight pipes and pods, I made custom inlets for it and it has a mikuni VM 22 (PZ26) on each cylinder. Can’t get it to run well! I’ve balanced the carbs at idle with a Carbtune 2 Pro, and set the mixture with a Gunson colourtune after watching this video (the Carbtune and colourtune are awesome so thanks for the recommendation!) ....got good strong sparks and bunson blue bang when I look down the cylinders with the colourtune..... BUT if I rev it at idle with the Carbtune connected the front cylinder is pulling a ton of vacuum while the rear one drops off to nothing, and when riding it’s absolutely gutless, bogs out at anything over quarter throttle and stalls constantly when coming off the throttle. Front exhaust gets hot as hell too! I’ve pulled the plugs and they’re sooty which would indicate a rich condition but I’ve tried smaller pilot and main in both carbs and it’s not improved it. Currently have 95 mains and 12.5 pilots. Do you have any suggestions? I’m losing the will to live with the thing right now! Considering binning the twin carb setup and going to a single PZ30 or something unless I can get to the bottom of this 🤦🏻😂
Masterclass! Thanks - just learning about all this as I am far more interested in carbs and cables than injectors and pulses. I was wondering if you set (colortune) the air/fuel on idle, does that setting carry-over to other circuits too? There's no real way to tune the idle, needle/jet circuits independently right? I did look into wideband AFM's but it's back to computers and - meh. Also (sorry) how much revving can you do with a colortune? Not much? Thanks - off to binge the other videos now.
Hello, have a question. I did carbs sync by using tachometer. I runed bike on the main carburetor and adjusted idle around 1000 rpm. than i runed bike on second carb it was around 2000 rpm and I tuned screw till it will get 1000 rpm too. Then I runed on both carbs and everything was looks fie. Is it normal approach?
Hey! I'm a newbie and this video TOTALLY HELPED ME! However, due to lack of expertise and void of mechanics capable enough to change jets, I can't help but stick to the stock jets. I've a free flow slip on and a k&n filter, however, as you listed 3&1/2 turns or more would require upjetting, my bike requires close to 7 turns (fuel control) Can I run my bike on these settings, or will it cause any harm? There's slight pops on decel but they're controlled and nothing excessive. I do think the bike heats up slightly but I'm thinking that's due to it being air cooled and me sitting in the parking lot for extended durations tuning it correctly. Your response would be highly appreciated as to if I can continue with my current setting. Thanks! Also, at the point where engine rpm is at it's peak, can I open the screw (fuel control) 1-1&1/2 turns more just to be on the safer end of the spectrum and keep it rich? Your reply would mean a lot :)
Now, what needs to happen if the bike runs, but it bogs down a little when you hit the throttle? Are the carbs not synched or does the carb mixture just need tuned? Thanks for the help!
Andy, thanks for the video. I’m hoping you can help me diagnose a problem-I have fuel leaking into the airbox and also discovered there is fuel in the crankcase. Obviously that’s a big issue. Why is it flooding? Wanting to do pods, and jet/tune the carbs, but need to ensure I have stopped the fuel leak. Real pain to consistently replace the oil. Thanks, Andrew.
Sorry for the late reply, I often introduce a self imposed black out. The leak is a result of leaking fuel taps. The static head pressure in the tank is often enough to bleed fuel past the needle and seat. It finds its way into the airbox and engine via the air correction jet and even the needle jet, especially when it is sitting on the side stand. It floods into the intake ports and enters the engine via whatever intake valve is open. It is not good because it will washout your bearings, not to mention the flammability issue. Root cause is usually either a leaking fuel valve vacuum diagram or the liquid seal itself. Also possible that it is the octy valve if it is an XS11. Have a look at my video on the GS fuel valve, it may help you understand the issue ua-cam.com/video/DpniuDh_TFI/v-deo.html
Thanks, this is helpful. I have a 1980 XS11G, though I believe a previous owner install at Special Tank and petcocks. The petcocks appear to be rock solid and not leaking. Also-I have bypassed the octy. I just capped off the two front nipples. I also was able to start the bike up recently and don’t think the carbs are leaking anymore (after a good clean) but the bike cannot hold idle. The moment I stop giving it gas, it dies. Even if carbs are leaky, I suspect it should be able to idle. Do I need to test for compression? Hoping I didn’t harm the engine when there was gas in the oil.
You think it runs like shit now, wait until you fit pod filters 😂 Seriously I would advise sticking to the factory airbox. That aside I would say that if you are certain that your fuel valves are all not leaking then I would be double checking your float levels and the needle and seats. As for the not idling it is possible that you just need to adjust the air/fuel mixture (more enriched) or that your butterfly shaft seals are leaking, or some other vacuum leak. Get it running and as close to idle as you can. Then spray some carb clean around the shafts and the manifold boots. You will hear the RPMs pick up if you have a leak. *Edit* also check valve clearances
Hi Andy, do you perhaps have a bike with a 4x rack KeihinCVK32 carbies on them? Would really appreciate it if you could do a video on the tuning of them just to get a hear for the sound when almost set, it is very hard for me to hear what sound im looking for as 4x together is very difficult to hear, just the sound it should sound like when in the ballpark. I have a Kawa GPZ600 A1 '85. Carbs are synched, but when i set to factory as per manual it stalls as soon as i touch the throttle, full choke makes it run better so I assuming it a bit lean, all jets etc is stock sizes, bike also stock, just 4 into 1 exhaust change, stock airbox, new filters, valves adjusted and so on. Any help to 'hear' n good tune would be very much appreciated.
Do you have to let the middle cylinders run a little richer on idle as well? On my oil cooled kawasaki, the middle cylinders have bigger jets, so that they don't run as hot as the exterior ones. It doesn't say anything about adjusting the idle screw different, though
Andy, a great video there mate! I have a question about the Digisync device. If you have the 4 channel model and wish to balance the carbs on a twin, will it work? Do you need to have the model specific to the number of carbs? Many Thanks
Just rebuilt my carbs on my Kawasaki Concours C10 with the CVK32 carbs. I'm considering eliminating the airbox and going to can filters. How difficult is it to rejet and then tune? Thanks
+Joe Simmons CV carbs will run with pod filters, but you will struggle to get them to perform and will regret removing the air box ultimately. By all means try, lots of people have, but make sure you can put all the factory stuff back if it proves too problematic. The CV carbs are designed to compensate for various altitudes and as a result are extremely sensitive to change in pressure between the Venturi and the air jets, particularly the emulsion tubes. If you can maintain the same length air tract and deliver laminar flow, by using the factory intake tubes with the pods fitted to the end of them, you stand half a chance. But they rely heavily on the shared air plenum of the factory filter housing. I'm waffling now, thanks for watching and good luck with your project, Andy
What's your take on soaking the carbs in Acetone to clean off heavy varnish? Also, I've heard some putting small amounts of Acetone in the fuel to keep them clean. I'm less prone to do that than clean with it.
Hi Andy,I own a 78 cb750 f2 super sport which I've recently rebuilt the top end. Its also had an 836cc upgrade. My question is what size main jets do you recommend ? im using pod filters however I cant seem to get an even balance on take off and top gear. my original spec's say set the fuel screw to 1 3/8 out. I watched your video and have set to around 2 1/2 and 3 turns out.It runs great in 3rd to 5th gears however on take off its flat. Hope you can help.Thanks Dave.
G’day Dave. If it’s running well at wider throttle openings I would suggest that you first try lifting the needle one position. If you still have trouble try going up a size on your pilot jet
I have a 1982 Kawasaki kz 305crs it's stock is there any way to get more power out of it I get to 45-50mph and it just has a hard time going Amy faster I'm a new rider and have not had much time working on them any help would be awesome thanks
Damn I'm old and owned bikes with carburetor single cylinder, multi cylinder is FI. I never thought it'd be this hard to tune, my ears and timing is bad i wont be able to do this lol
Excellent stuff and well explained. But... I really got the shits trying to balance the carbs on my 72 Moto Guzzi Eldorado. Bloody things kept falling over, time and time again, probably due to being really top heavy and having too many round surfaces (probs didn't help that I'd just polished them, so reducing the co-efficient of friction of the surface). Out of frustration I ended up attacking them with my grinder to make some decent flat spots on the bowls, and viola! Unfortunately when I checked them on a fine set of weigh scales (not the cheap Chinese rubbish your friendly local drug dealer uses) I ended up being about 15 grams heavier on the port-side carb. This turned out to be even worse when I made the newbies mistake of changing the scale display from metric grams to Whitworth grams! So - would you recommend: A: Try to shave a bit more of the Starboard side carb with the un-precise grinder. (Bearing in mind that my grinder is from from Super-Cheep Autos, the ones which you can't change the disk on, and its getting a tad blunt). B: Gluing lead weights or similar to the Port carb at a point that would also have the advantage of balancing the centre of mass (and hence centre of inertia) of the carb? C: Buy one of those flash Ozito grinder from Bunnings and repeating "A". Thanks in advance. Dave P.S. Great job here and well explained, but just couldn't resist this after watching Ichiban Moto's latest release.
Hey Andy, the XS1100 is magnificent. I’m building up a late CB750 cafe racer at the moment. Planning to fabricate two 2 into 1 cylindrical airboxes with two big K and Ns to try and overcome the CV carb with four pod filter problems. Where did you get the small front mudguard.? I haven’t managed to find anything suitable and thought I might have a go at cutting down the Honda original.
G’day Tim, i bet you’re having a great time with the build, I know I did. I cut down the original, see it here ua-cam.com/video/qwNlQQuE6VQ/v-deo.html thanks for watching
I have a question. I have always been the guy who is passionate about mechanics cars bike motorcycles ever since i was a kid cuz we couldnt pay to have out stuff fixed but i learn as i go so im facing my fear of carbs today. I bought a project bike that looks much like yours a week ago. Its a 1982 xj11 i put a new engine in it got it all set up fired it up and it is revving at about 7000 rpms. I checked the idle screw and it wasnt even touching anything. Not completely knowing its purpose i looked up online where to set it i screwed it all the way in backed it out a half turn. Didnt help at all. I thought vaccume leak of some sort so i sprayed around with some starter fluid no leaks engine just roaring. I figure the carbs were "jetted" for air stacks and straight pipes. But the butterfly valves are shut or appear to be via idle screw fully loose. The engine ran fine when i bought it but the transmission was bad I got a deal for a whole new engine. I have to theories. The engine i pulled was modified idk how and set up for more fuel and carbs need adjusted or a vaccum leak i can not find. Its a month wait on the only guy in town doing carb work so i am just gonna figure it out. Now my question there is the idle screw you talk about at 9:01 but are there individual scews on each carb i think they adjust idle via the air fuel mix idk. Is that how i adjust the carbs? They have been recently cleaned and synchronized.
G’day mate, sounds like you’re at your wits end. Here’s a few things to look at. 1. If the idle adjustment screw (singular) is not touching anything and is high reving it is possible that your accelerator cable is not adjusted correctly. 2. Yes there will be an air/fuel mixture screw on each carb. Carefully wind them all the way closed and then wind them out two turns. Start there and see how you go.
Help !!!!!!!!!! Hey man so I have a question I need your help So I was riding home one day and I ran out of gas I turn my Petcock switch to reserve then I went to the gas station I didn’t turn the Petcock switch back to the on position The bike is working fine it’s seem to be at least I get back on the freeway and it works fine but ever since then if I try to hold high speed for long periods of time the fight starts to bog and will eventually cut off If I don’t let off if anyone knows anything please let me know it would be a huge help I have a Suzuki katana 2006 750
They’re somewhat more sedate in standard trim. This bike has extensive cylinder head work, a big bore kit, the RS36 race carbs and four into one with not much muffler.
Hi Andy, Bloody brilliant videos. I've got almost all of my XS1100 knowledge from you and Basket Case. What's the difference in hose and adapter sizes for? I have an '80 xs1100 stock carbs and I'm looking at purchasing the digisync as I've had problems with them. Which would I need? Many thanks, Greg
Hi Greg, the adapters are for manifolds with screw in ports. As the XS1100 has tubes mounted in the manifolds you don't need any adapters. You just remove the rubber plug from the manifold and push the hose straight on. Thanks for watching, Andy
G’day mate, I use a MotoGadget M-Lock ignition. It uses a RF reader to switch on and off. I was waving the fob past the reader, which is located below the seat, and I placed the fob on the lift.
Andy i need your help, I have a 1978 xs 1100 ,i took off the airbox and fitted 4 k&n filters Ran ok ,BUT now when the bike runs i have petrol pumping out of the airtubes that where connected to the airbox. I cleaned completely the carbs ,but petrol still pumps out!!!!! I cant think of anything it could be ,any ideas???? Thanks in advance ,ride safe !!!! Cheers mate !!!!!, bye
G'day Andrew. The factory carbs run far better with a shared air plenum, a lot of engineering went into that airbox. That being said it shouldn't be doing what you're describing. The short answer is that they are flooding, those airtubes are the float bowl breathers. The task for you now is to work out why. It will be fuel bypassing the needle and seat and it could be for a number of reasons. It could be that the needle and seats leak. It could be that your float level is set too high, it could be that one or more of the floats are being impeded by something within the bowl and are unable to operate properly and close the needle and seat. Watch my video on bench tuning a set of CV carbs from a GS1000, the process is the same. ua-cam.com/video/8p7s6U9HMoE/v-deo.html
@@ANDY5 ,thanks for the immediate answer Will watchsaid video ,go through the process, and report back Take care See you on the road (huh, your in tasmania and im in france!!! ,you know what i mean) Cheers again ,bye
Im look for a tune.. adjustment.. First of all my bike is really old.... so There is some sett off. 2nd of all. The bike was Made for leed gas.. back in 1996. And NO ethonal... Thats the perfect tune......... For last 13 years we have here in sweden 5 % ethanol okey fine thats not match..... That Will be Lean by just a snitch.... But son this year 2021 it Will be 10% of ethanol! Thats really alot.. Well usa have That for long time but not me in sweden....... How do i do whats needs to do ? Now When they put 10%.... Do i need to adjust the needel? One up or down ? Do i need some bigger or smaller jets?
My bike only runs with starting fluid and it revs up to 6k when I start it n don’t touch the throttle. My carb boots look a lil cracked but not on the inside so idk
Does anyone know if there are any main and pilot fuel jets from other carb manufacturers (ie: Mikuni, Keihin, ect.) that can be substituted for use in the Hitachi HSC 32 CV carbs used on the 80-82 Yamaha XJ650?
due to a family crises Dynojet is out of my price range right now. because the original stock jets were kinda beat up I replaced them with new stock jets along with all the other parts you normally replace in a rebuild, I even checked to make sure the jets were the actual correct size but bike still running way lean when not on pilot circuit so just to try and get the bike to run richer above 3000 rpm I increased mains all the way up from stock of 110 to 116 which made the bottom end run so rich that it stumbles all over itself but above 4000 rpm's the bike goes dangerously lean equally on all 4 cylinders. Ive been working on bikes for 40 years but don't have much experience with CV carbs, there has to be something I'm missing so I'm hoping someone might have some other ideas beyond the obvious ones. thanks for responding though....
I don't think absolute accuracy is necessary to balance the carbs, only that each input reads the same, or that if there's a variance that you take note of it. You're looking at relative changes, nothing more. I used this and found it worked great: www.carbtune.com/carbdtls.html Much better than that Motion Pro thing that lets all the fluid into your engine if you blip the throttle a little bit too much!
The guy I just sold my SV to. I spent a good 3 hrs walking him through the carbs & fueling, how to disassemble the fuel system & where everything was, why? because I knew & he wanted to know. as bikers its our duty to pass on info to those willing to try. great vid man.
+gizzy nc thanks mate, as a fan of older bikes I feel we need to help where we can to keep them on the road.
especially since once all the electronic fuel injected bikes have fallen apart, the old bikes will still be running in the mad max like dystopian future.
@@HypnoticPattern And we'll need to tune them to run on the remaining stale fuel
6.17.22. Learn it, use it, pass it on!
I’ve built and worked on motorcycles for over 50 years. Even I enjoyed this!
Fantastic explanations. Appreciate how you explained things more in layman’s terms. I’m one of those guys that I’m still learning mikuni flat slide bst 36s. Been a challenge. Still trying to fine tuning. The fuel air jets at 1.5 turns out. Thank you
At last, someone who doesn’t refer to the whole world as ‘guys’ and isn’t wearing a baseball cap backwards.
Thanks for the intuitive explanation of how to tune carbs.
Much appreciated.
Andy, thanks for the info! You made it super easy to understand how to tune a carb!!! I've rebuilt and tuned carbs on cars but never a motorcycle.
I don’t think any video I’ve watched on carburetors has ever told me anything I didn’t know or was any help to except this one this guy is awesome thank you for this video
Many many tears ago I worked in a large bike shop in Sydney, I had many many young blokes come in to buy a power band. The first was quite funny but after that we had a little spiel to help them understand what it was, what a reed valve was and how jets and cutaways worked. Most of those guys were dirt bike guys with two strokes and I think they mixed up the new reed valve technology with discussions about power and performance etc. yes, it our job to help our fellow riders understand and learn. After all it really is true that every day is a school day.
FLAT SLIDE CARBS, so cool and so tuneable for peak performance.
Thanks just about to tune and sync my triumph tiger 1994 has been stood for 20 years but only 7000 on the clock now I know how good man
Incredible video, really got right in the nitty gritty of what tuning does, what can be tuned, and (most importantly) how to do the tune.
Just used a 4 dial vac gauge on my XJR1200, lots of fiddling around, the workshop book never mentioned a master port to work off of, just said to sync them all the same with idle set or adjusted after each change was made. I came to the conclusion it ran pretty much the same but tick over was a bit smoother. Lovely bike you have there btw!
Good on ya. Much appreciated. I've "sync'd" Carbs on a VW years ago and many on cars/trucks but never cycles. This vid made it all make more sense.
+james woodend thanks for watching James
excuse my language but this video is fucking awesome, haven't finished it yet but i had to stop and write the comment. I'm not a novice with carburetors or engines but i know how to do stuff, not necessarily why things act or work the way they do. It's good to find videos that show why problems happen and why solutions work not just instructional videos and how to
Thanks mate
That sound is just wonderful!
This is great. You have an awesome attitude towards education. Its much appreciated.
Thanks Andy. New to bikes 🏍 but I have 25 years of mechanical engineering experience. Sure helpede wrap around my carb project
I tried making a homemade synchronizer with a plastic bottle and clear plastic tubing with auto trans fluid. Didn't know how much vacuum the Mikuni's pulled so it didn't work. (Yes, I shut the engine off after seeing the fluid about to go into the carbs.) Bought a 4 gauge sync at a local bike shop for $60 and it's one of the best investments I've made. Time to work on the wife to get me a colortune!
Most of the Ninja's i have owned recommend 2 1/2 turns outwards on the air/fuel mixture screw, as stated in factory manual
This video really helped me to understand how to tune carburetors. Thanks!
THAT'S A GOOD ILISTRATION, Of the carbs anyone CAN Understand, GOOD JOB, ANDY...
sounds better and better ever time.. great explanation to Andy
Thanks Brian
Man watching you CRANK on your carb sync screw was WILD...Man that's some TIGHT screw!
Thank you sir for sharing your knowledge you just gained a subscription
Great video. I think the confusing part for some folks is the terminology. I use the term 'balance' to describe the gas to air mix for each carb and 'synchronize' as the term to describe adjusting the carb butterflies to be the same.
Hi Andy, my second name is the same, & some friends only know me by that name.
I have been following & really enjoying your posts, especially those of the XS 11. I have a 79 XS 11 F, bought as new. It has done 46 thousand kilos, but has been standing 12 years now, due to it having caught alight in 2006, minimal damage though. I had added carburettor cleaned to the fuel, & unfortunately there was a minute rust hole held closed by the paint all the years, which was opened by the carb cleaner, which allowed the fuel to spray onto the plugs, hence the fire.
Unfortunately I left the fuel in the carbs for too long, & as a result minute holes were eaten into of the brass floats, & the carbs were a mess when I eventually opened them up! I found Acetic acid cleans the brass very well but doesn't eat any metal, even the aluminium.
I retired at 65 last year, so now have time to do some minimal "rebuilding" of my bike to get it back on the road. Fortunately I'm still very much on my feet, young at heart, & able to still enjoy my bike when it'll be back back on the road. Its still in a very good condition.
Just one question ... What would be your opinion regarding its bores? Do you think I need to open it up to check on rust? I I've in Port Elizabeth South Africa, maybe a climate similar to you side?? The bike has always been well covered in the garage, the inlet ports stuffed with rags. I do maybe have to replace the valve guide seals, as it used to burn an oily sediment on the exhaust end, but that I could see, it didn't smoke. Maybe I should just open it anyway, replace the oil seals, although I'm keen to ride the bike. I do remember that if it stood long, it would smoke after standing, but once warmed up would stop smoking once warm and started a second time, so probably valve guide seals?
Not sure if you're still posting, as Uve only recently discovered your posts and enjoy them, they're interesting & informative, just great!
Go well!
@@michaelbutlion5087 are you back up and riding ...???
@@jerryking1434 Hi. Unfortunately I'm not anywhere near that yet. I'm a member of the Triumph Sports Car Club, Port Elizabeth, the name now been changed by this idiotic government to some other unpronounceable name, here in South Africa. I've been working on a club member's cars, the last of which I hope to give back to the guy by the end of next week.
Only then am I going to be able to look ahead at my very patient bike that I'm dying to get back onto!
In the meantime I've progressively prepared and planned ahead and should have everything ready to start immediately once my other commitments are cleared.
Its been a long wait!
Champion mate. I got a 85 1200 Goldwing and running a little rough. I like the look of the digi sync.
Would you recommend a zephyr 1100 with 7000km today? Are they relaible bikes?
Top bloke nice n relaxed presentation, great vid. Please be careful where u place music, we need to hear u and all 4 cylinders :)
We moved to a higher elevation.. from 1000 ft So Cal to 4600 ft Arizona ... runs kind of ragged.. My issue is I have both fuel and air pilot screws. Mikuni VM28SS on '79 Suzuki GS1000EN.. I'll keep working on it until it's right, but your video simplifies the process very well. any general tips? I really don't want to re-jet if I can get by without. None of the bike shops around here work on these old carb bikes.. at least for tuning... thanks..
Another great video Andy, i have mounted the Brembo conversion on my xs1100 since i last commented. Turned out to fit absolutely perfect. No caliper clearance issues at all and mounted up to the forks easily with the supplied bracket. Now i need to run my brake lines and finish that up. The wiring on the bike is still a nightmare
+Ben Hebert that's great news about the calipers, not so great about the wiring 😐 thanks for watching
do you have any remedy for a really heavy clutch. mine is extremely firm and is a workout to pull.
If you are using aftermarket levers you may not be getting the mechanical advantage you need (the XS11 clutch lever is very long). If you have heavy duty springs in your clutch you can try replacing two, diagonally opposite, with standard springs. Other than that all I could suggest is clean and lube everything, including your cable, and make sure that the cable isn't being impeded anywhere. Maybe some time in the gym lol.
Thanks for the speedy reply i love watching your videos. i got some used carbs on ebay which were surprisingly clean and look like they're in way better shape than the ones my bike originally had. the wiring is still a bit of an octopus. Wiring it with the motogadget m-unit is proving to be harder than i thought. i got the starter to work by running wire to the switch but thats about it!
Thanks Ben, if I had known about the M-Unit when I started this project I would have bought one. I hope you sort it out.
I have a 1981 Yamaha xj750 and rebuilt the carburetors, but now it runs worse, doesn’t even want to idle and when I hit the gas, it drops down and then revs up. Do you think it needs to be synced?
Hey! Just wondering if you ever found the answer to your question, because I am having the same issue with my 1986 Kawasaki ZL600. Thanks!
Just watched. Great video and explanation.
Subscribed. I have a 83 XL600R single with 2 carbs, but they don't have to be synced. My 79 R100 is a different story. Great vid.
Man that bike sounds incredible. Great video.
Thanks for the video. I like how you know what you're talking about.
I’ve been having issues with either fuel or air getting through. My tanks dirty but I’ve cleaned it and also cleaned the carbs (carbs have always looked fairly well inside no clogs at all just some settlement at the bottom) however the bike surges at idle and while riding. When you choke it it sets at 2000 rpm am slowly he’s up to 3-4 and then drops back to 1. If I play with fuel mixture screw it’ll stay running at the cost of hanging revs. I just had it tuned not long ago but it already sounds like crap again
Fantastic video, very well explained, thanks for the help.
Hi Andy ! As i promised, i came with my questions. I think it will be more easy for you if i just leave what i have done, changed on bike and my current problems, so you can have a diagnosys of your own. Because, obviously besides you, my mechanical skills and knowledge cry outs :D
It was a 22 year old GN 250 working fairly good. (Had some prolems on carb)
I'm skipping visiual changes, focusing on mechanical ones
So;
1. As soon as i bought it, i have done a top end rebuild with 300 cc BBK. Replaced clutch plates, valves, starter motor, rectifier, air filter, all fluids and tyres etc..
2. It worked pretty well (it still works), i achieved my goal which was increasing the torque of it. And i replaced the sprocket combination from 15/41 to 15/38. Also changed the slip on with a new one which is almost same as the old one in back pressure manner, but of course looking better...
3. After a 500 km running in breaking process, i gave it a full throttle to see the top speed. It was about 110km/h on 5th gear. I was pretty unhappy about it because original set up could do 130 in good condition. I have observed it very carefully and saw that it won't go above 6.500 rpm.
4. So i decided to change the main jet as usual and did it from #130 to #135 and pilot jet from #40 to #42.5 ( i had lots of bogs at mid rpm. with that change it all gone and now it's bumber and smooth at mid rpm/throttle position) It didn't matter so much. It just ran smoother. Also, replaced the spark plug with the same numbered iridium one. No improvments.
5. Then i took of the air filter from the box, boom, the torque was raised by God's hand, but still no improvment at high rpm on 4th and 5th gears. It just won't go above 6.500, even getting there so hard. Btw, there is no problem on 1th, 2th and 3th gears. I see 8.500-600 rpm which is the enter into red line for GN250s.
I checked the diaphram and slide on carb and there was no prob. But still to be sure, i got a new one. I didn't put it yet. Also i bought an Apexi air filter that is waiting for putting.
It starts at first attempt in cold wheater. Just won't go above 6.500. Even it arrives there pretty hard. Maybe it will go above 6.500 like 7.000 but down the hill.
Thank you in advance...
Btw, i have bs34ss mikuni carb on it as genuine. Waiting for you wise aproach :)
Hi Ali, I will sit down, read and digest this when I did some time to focus on it. We are heading interstate this week and are doing the family Christmas thing this weekend with the grandkids etc. I promise I’ll get back to you soon, Andy
Thanks Andy, cant wait to read it ! Wish you and your family Merry Merry Christmas !
I haven’t forgotten you mate, I’m just a bit busy at the moment. Probably won’t have time to focus until after Christmas
Andy's Motorcycle Obsessions Don't worry Andy, I have time and in mean time I will let you know about the upgrades that I'm going to do soon. Thank you a lot, I have already learned a lot from you. Waiting for your wise advices ! Cheers ! (BTW, I'm from Turkey and if you need anything related to my country, I'd be happy to help. Just letting you know) Have a nice day, I'm going to sleep now :D
thank you. carbs are bit handfull for me, but this helps a lot.
Glad it could help. There are a number of carb videos on my channel mate, thanks for tuning in.
VERY ULTRA COOL,... so nicely explained and done.
Legend Andy! Thanks mate!
Great video. Since i seem to have a little issue with My carbs. This video just came handy for me. Thanx
Can I swap the hitachi that comes with my XJ750 for better ones?
I look up a Video on tuning Carburetor's and the dude is working on my engine. Convenient I suppose.
Different Carbs though lol.
Id like to try one of those Colortune plugs, but cylinder 2 and 3 are a pain in the ass to get to on my 1975 CB750. Seems like it would be hard to check those two, even with that mirror tube thing it comes with. I could do 1 and 4 easily. I have a Morgan Carbtume Pro for my syncing, which works well. I'd like to try the DigiTec out at some point.
I've got rs34's on my cb 750 and they are a total nightmare to balance, even when you did your correct adjustment and go to lock it down with the locking screw the adjusted is knocked out
I hate carburetors after having a fuel injection. I just sold my last of many motorcycles with carburetors. Now all my motorcycles have fuel injection..I won’t miss vacuum diaphragms, nozzles, needles, needle clips, needle and seat, floats, pilot jets, air screws, atomizers, enriching circuits, chokes, main jets, ticklers,.. I remember trying to synchronize for carburetors on the 1969 Honda CB 750 with vacuum gauges. Each carburetor had its own cable. You could get all the carburetors close to balanced, then blip the throttle one time, and they would be all screwed up..I remember having to jet my route race machines for racing at mid Ohio, then having to go fat for daytona jetting at sea level..
You had to carry Jets to change for elevation went dirtbike riding in the Rocky Mountains . you had to pull over and put in a leaner main jet the higher you went in the mountains.
then there were the Suzukis of the 1980s. You simply could not get those machines to run correctly with the EPA doing the jetting for them. many of them were so lean, they would actually slow down if you shifted into sixth gear wide open. They would go faster in fifth gear with the choke partially on..And that was at 1400 feet of elevation. I can’t imagine how poorly they ran at sea level..
I will not miss carburetors ..
Varying altitudes is the reason CV carburetors were invented. Technology has come a long way.
Andy's Motorcycle Obsessions
of course, CV carburetors do compensate somewhat for altitude. But, none of my dirtbike‘s had CV carburetors. Not my YZ 125, RM 125, CR 125, CT1, CT2 IT 175, IT200, KD 125, KDX 175, KDX 200,(Air cooled), KDX 200, water cooled, DR 100, YT 175,Gas gas jtr250,fantic section 250,BETA jtr 250, XR 250 R, XL 250,tt500...
none of my above motorcycles that I have owned from time to time since 1968 have had CV carburetors..And these are just the off-road dirt/trials bikes that I have owned. for street & RR track,into the RDs, cb750,cb400f,z1,DS7,R5,RZ350,H1,S2,A1,A7,350GTR,TZ250D (with lectrons)TD1,td2b,H1-R(yes a sand cast case dry clutch factory Kawasaki H1R-eric buell ended up with the chasis)
None of these machines had CV carburetors either
I have owned every one of the above machines.. these are just most of the ones I can remember without CV carburetors..They really make me appreciate my fuel injected machines, my current street bikes are a Moto Guzzi Norge, and a Honda GL 1800
.. when I was a Honda motorcycle mechanic at a busy dealership that had seven full-time mechanics. I remember that I bought my current snap on 24 inch number two Phillips screwdriver, just for pulling the carburetors on CB 750s..I remember what a pain in the ass it was to sinc The first generation CB 750 carbs when they each had a single separate throttle cable before bell cranks..
no I do not miss carburetors one bit..
I actually had one 1982 Suzuki DR 100 4-stroke, My wife’s trail bike, a California model. I could never get that motorcycle to carburate correctly.. it wouldn’t run unless you left the enriching circuit on for three or four minutes and let the motor rev without touching the throttle for the first five minutes. Then once it warmed up, trail riding, climbing a steep hill, it would pull, until you went to three-quarter throttle, from 3/4 to wide open, it fell on its face/lean. Let off the throttle, it would start pulling again. I tried needle shims, I tried main jets, I tried , everything I could think of, that California turned by the EP a carburetor could not be made to run correctly. It was not the float setting,, It was not an air leak, it was not low compression, it was not a tight valve. It just went Lucas
Thanks Andy!
Hi, I have both a Intruder VS1400 and Marauder vz800,,,I have the bikes running well and synced,,,However the idle on both of these bikes is a bit off,,,AND upon bliping or reving the throttle on both bikes the idle hangs for a sec before returning to steady idle,,,from my under standing when this happens its typically a lean condition, conversely when you blip a throttle and it dips, then returns to idle its a rich condition,,,,,,,IS this issue solved by simply finding the correct mixture screw seting on both carbs? IF not do you have any other ideas for me to try? TY you have a great channel
thank you it was very informative
I've got some of same stickers; ngk k&n, an I member my brother jokingly try to convince his friend to balance his carb! Haha! While they were raddle can spray painting his 51 chevy an Orange color.
Hiya,
I have a 1987 CBR 600F1 that I rebuilt the carbs in. I had a heck of a time getting them adjusted to what seems right. The float heights were difficult to set only due to being confused about the seating position as the Clymer manual was pretty vague. The bike seems to work fine, but I can't tell if its warming up properly or not. I want to say it IS, as the manual states that it takes about 10 minutes of stop-and-go riding to warm the engine up properly, but I can't be so sure as I have no good reference point. I don't like to hop on it early unless I keep the enricher partially engaged as the bike is very easy to stall otherwise but only takes a few minutes of riding until I can turn it off safely. The bike doesn't overheat and it runs at normal temps while idling (3/4 temp gauge) and while riding (1/2 temp gauge or lower.) My other bikes (2007 ex500, 2000 sv650) warm up to riding temps pretty quickly in comparison.
Another issue I am having is I have a very very slight stutter at about 1-5% throttle and only if I turn the throttle slightly, but quickly. Almost as if there is a very small delay. Any more than a quarter of a second and the bike revs up just fine. Is this potentially a rich condition at that point of throttle? I've heard of someone else solving by using a slightly larger jet (on a different bike,) but I can't be sure that my issue is as severe as theirs.
Finally I have one more issue . . . if I perform a hard stop my rpms will drop and the bike will stall. It immediately starts back up. I figured this was just the fuel rushing to one side of the carbs due to the nature of hard stops, but should this be a problem on this bike? Some others have agreed with me, but this is the only bike I have that exhibits this symptom :/.
FWIW - stock jet sizes. Illinois weather (riding in 18-60 degree weather) and parts unlimited brand rebuild kit. Float adjustments were done using a high quality metal ruler and digital caliper after finding other tools to be less accurate. Adjustment screws on each carb were set at manufacturer recommendations.
I installed a Jet kit in my sv650 and synced the carbs prior and it runs like a top.
Have you considered that your ignition timing or advance my not be correct? Many of your symptoms could indicate this. There is an old bike mechanics saying, "90% of carburetor problems are electrical". It might be worth looking into.
Thank you! Unfortunately I am not experienced with engine internals, but when its warmer I will flip through my service manual and see what I come up with. My eventual goal with the CBR is to get a 1990 model in OEM paint and install all of the factory pro upgrades - jet kit, ignition advance, etc. to make it as good as can be. Thanks again!
Luckily, here in the UK at the moment we have E10 or E5 petrol, (10%) or (5%) Ethanol, because my bike is 2004 I remove the Ethanol anyway and add an additive to boost the octane back to what it was originally.
why is the air/fuel mixter goes lean when the throttle is closed? i dont understand
Hey, thanks so much! I've got a question: I've seen a video of a guy who disconnects the spark plug from one side of a v-twin, in order to set each carb individually. In my mind that makes sense, since you eliminate any influence by the other carb. However in most videos I've seen by professionals, they let both carbs run. Is there a reason for this, and are there any risks involved with setting one at a time? I'd much appreciate some wisdom on this.
Hello Andy,great videos. They are extremely helpful. I have a gs1000l and am having problems with #3 carb. I followed your videos cleaned and put new kits in them. The engine ran decent but no matter how much I adjusted #3 nothing changed. I took Temps on all exhaust pipes and found #3 was twice that of 1,2,and 4. Meaning a leaking condition. So I'm thinking #3 carb is plugged somewhere. I was wondering what your thoughts on this problem is,could really use your input. Thanks
can the colortune be used with deep recessed plugs , for example a suzuki 1200 bandit
Alright Andy!
I need some assistance....looking for carb/jetting advice to get my twin running right before I roll it off a cliff! 😂
250 V twin Yamaha, running straight pipes and pods, I made custom inlets for it and it has a mikuni VM 22 (PZ26) on each cylinder. Can’t get it to run well! I’ve balanced the carbs at idle with a Carbtune 2 Pro, and set the mixture with a Gunson colourtune after watching this video (the Carbtune and colourtune are awesome so thanks for the recommendation!) ....got good strong sparks and bunson blue bang when I look down the cylinders with the colourtune..... BUT if I rev it at idle with the Carbtune connected the front cylinder is pulling a ton of vacuum while the rear one drops off to nothing, and when riding it’s absolutely gutless, bogs out at anything over quarter throttle and stalls constantly when coming off the throttle. Front exhaust gets hot as hell too! I’ve pulled the plugs and they’re sooty which would indicate a rich condition but I’ve tried smaller pilot and main in both carbs and it’s not improved it. Currently have 95 mains and 12.5 pilots. Do you have any suggestions? I’m losing the will to live with the thing right now! Considering binning the twin carb setup and going to a single PZ30 or something unless I can get to the bottom of this 🤦🏻😂
Masterclass! Thanks - just learning about all this as I am far more interested in carbs and cables than injectors and pulses. I was wondering if you set (colortune) the air/fuel on idle, does that setting carry-over to other circuits too? There's no real way to tune the idle, needle/jet circuits independently right? I did look into wideband AFM's but it's back to computers and - meh. Also (sorry) how much revving can you do with a colortune? Not much? Thanks - off to binge the other videos now.
Hello, have a question. I did carbs sync by using tachometer. I runed bike on the main carburetor and adjusted idle around 1000 rpm. than i runed bike on second carb it was around 2000 rpm and I tuned screw till it will get 1000 rpm too. Then I runed on both carbs and everything was looks fie. Is it normal approach?
Hey! I'm a newbie and this video TOTALLY HELPED ME! However, due to lack of expertise and void of mechanics capable enough to change jets, I can't help but stick to the stock jets. I've a free flow slip on and a k&n filter, however, as you listed 3&1/2 turns or more would require upjetting, my bike requires close to 7 turns (fuel control) Can I run my bike on these settings, or will it cause any harm? There's slight pops on decel but they're controlled and nothing excessive. I do think the bike heats up slightly but I'm thinking that's due to it being air cooled and me sitting in the parking lot for extended durations tuning it correctly. Your response would be highly appreciated as to if I can continue with my current setting. Thanks!
Also, at the point where engine rpm is at it's peak, can I open the screw (fuel control) 1-1&1/2 turns more just to be on the safer end of the spectrum and keep it rich?
Your reply would mean a lot :)
is there any disadvantage to running cone filter over a stock air box?
love the video's, as a fellow tasmanian keep them coming!
Thanks George, north or south?
south, based near the city. recently got my licence with some friends and have been enjoying your video's between riding!
You're welcome to join us on a ROT ride anytime mate
great info I'm new to the motorcycle world this was really helpful
Now, what needs to happen if the bike runs, but it bogs down a little when you hit the throttle? Are the carbs not synched or does the carb mixture just need tuned? Thanks for the help!
That’s generally caused by being a little too rich. It maybe worth dropping the needle position by one increment.
Andy, thanks for the video. I’m hoping you can help me diagnose a problem-I have fuel leaking into the airbox and also discovered there is fuel in the crankcase. Obviously that’s a big issue. Why is it flooding? Wanting to do pods, and jet/tune the carbs, but need to ensure I have stopped the fuel leak. Real pain to consistently replace the oil. Thanks, Andrew.
Sorry for the late reply, I often introduce a self imposed black out. The leak is a result of leaking fuel taps. The static head pressure in the tank is often enough to bleed fuel past the needle and seat. It finds its way into the airbox and engine via the air correction jet and even the needle jet, especially when it is sitting on the side stand. It floods into the intake ports and enters the engine via whatever intake valve is open. It is not good because it will washout your bearings, not to mention the flammability issue. Root cause is usually either a leaking fuel valve vacuum diagram or the liquid seal itself. Also possible that it is the octy valve if it is an XS11. Have a look at my video on the GS fuel valve, it may help you understand the issue ua-cam.com/video/DpniuDh_TFI/v-deo.html
Thanks, this is helpful. I have a 1980 XS11G, though I believe a previous owner install at Special Tank and petcocks. The petcocks appear to be rock solid and not leaking. Also-I have bypassed the octy. I just capped off the two front nipples.
I also was able to start the bike up recently and don’t think the carbs are leaking anymore (after a good clean) but the bike cannot hold idle. The moment I stop giving it gas, it dies. Even if carbs are leaky, I suspect it should be able to idle. Do I need to test for compression? Hoping I didn’t harm the engine when there was gas in the oil.
You think it runs like shit now, wait until you fit pod filters 😂 Seriously I would advise sticking to the factory airbox. That aside I would say that if you are certain that your fuel valves are all not leaking then I would be double checking your float levels and the needle and seats. As for the not idling it is possible that you just need to adjust the air/fuel mixture (more enriched) or that your butterfly shaft seals are leaking, or some other vacuum leak. Get it running and as close to idle as you can. Then spray some carb clean around the shafts and the manifold boots. You will hear the RPMs pick up if you have a leak. *Edit* also check valve clearances
Thanks Andy, Motorbike show wants £160 to balance the carbs on my cbr 600 f3 and like every true biker, we love to tinker with our bikes,
Those are not the OEM carbs.... What carbs did you use as your upgrade?
Mikuni RS36 Flat Sides
Hi Andy, do you perhaps have a bike with a 4x rack KeihinCVK32 carbies on them? Would really appreciate it if you could do a video on the tuning of them just to get a hear for the sound when almost set, it is very hard for me to hear what sound im looking for as 4x together is very difficult to hear, just the sound it should sound like when in the ballpark. I have a Kawa GPZ600 A1 '85. Carbs are synched, but when i set to factory as per manual it stalls as soon as i touch the throttle, full choke makes it run better so I assuming it a bit lean, all jets etc is stock sizes, bike also stock, just 4 into 1 exhaust change, stock airbox, new filters, valves adjusted and so on. Any help to 'hear' n good tune would be very much appreciated.
Thanks Andy! this has help me a lot!!! Mucking around with a Yamaha Scorpio at the moment. Almost got the carb balanced on it... ;) just kidding haha
lol...thanks for tuning in mate, Andy
Do you have to let the middle cylinders run a little richer on idle as well? On my oil cooled kawasaki, the middle cylinders have bigger jets, so that they don't run as hot as the exterior ones. It doesn't say anything about adjusting the idle screw different, though
G’day mate, quite common to see different emulsion tubes etc in the centre carbs. But no, you adjust the mixture screws the same.
Andy, a great video there mate! I have a question about the Digisync device. If you have the 4 channel model and wish to balance the carbs on a twin, will it work? Do you need to have the model specific to the number of carbs? Many Thanks
G’day Kev, yes it will work on combinations up to four cylinders, it is also available for up to six cylinders.
Andy's Motorcycle Obsessions Awesome, cheers Andy 👌🏻
Amazing.
Just rebuilt my carbs on my Kawasaki Concours C10 with the CVK32 carbs. I'm considering eliminating the airbox and going to can filters. How difficult is it to rejet and then tune? Thanks
+Joe Simmons CV carbs will run with pod filters, but you will struggle to get them to perform and will regret removing the air box ultimately. By all means try, lots of people have, but make sure you can put all the factory stuff back if it proves too problematic. The CV carbs are designed to compensate for various altitudes and as a result are extremely sensitive to change in pressure between the Venturi and the air jets, particularly the emulsion tubes. If you can maintain the same length air tract and deliver laminar flow, by using the factory intake tubes with the pods fitted to the end of them, you stand half a chance. But they rely heavily on the shared air plenum of the factory filter housing. I'm waffling now, thanks for watching and good luck with your project, Andy
What's your take on soaking the carbs in Acetone to clean off heavy varnish? Also, I've heard some putting small amounts of Acetone in the fuel to keep them clean. I'm less prone to do that than clean with it.
G'day Ryan, I've never tried it, I find that carb cleaner works fine. Thanks for tuning in.
Realy nice work !!!
Hi Andy,I own a 78 cb750 f2 super sport which I've recently rebuilt the top end. Its also had an 836cc upgrade. My question is what size main jets do you recommend ? im using pod filters however I cant seem to get an even balance on take off and top gear. my original spec's say set the fuel screw to 1 3/8 out. I watched your video and have set to around 2 1/2 and 3 turns out.It runs great in 3rd to 5th gears however on take off its flat. Hope you can help.Thanks Dave.
G’day Dave. If it’s running well at wider throttle openings I would suggest that you first try lifting the needle one position. If you still have trouble try going up a size on your pilot jet
Can i make my baterflyes from Carburetor Lauder???
Great vid bike sounds great Andy 😆
+Jim Aylward thanks Jim
man, i love that diagram
I have a 1982 Kawasaki kz 305crs it's stock is there any way to get more power out of it I get to 45-50mph and it just has a hard time going Amy faster I'm a new rider and have not had much time working on them any help would be awesome thanks
beast Castro get a bigger bike bruh
Fabulous! You got some mechanical carbs on there. What were you adjusting at the top?
The carb slide synchronisation is adjusted via a "cam" nut and locking screw.
Damn I'm old and owned bikes with carburetor single cylinder, multi cylinder is FI. I never thought it'd be this hard to tune, my ears and timing is bad i wont be able to do this lol
Excellent stuff and well explained. But...
I really got the shits trying to balance the carbs on my 72 Moto Guzzi Eldorado. Bloody things kept falling over, time and time again, probably due to being really top heavy and having too many round surfaces (probs didn't help that I'd just polished them, so reducing the co-efficient of friction of the surface). Out of frustration I ended up attacking them with my grinder to make some decent flat spots on the bowls, and viola! Unfortunately when I checked them on a fine set of weigh scales (not the cheap Chinese rubbish your friendly local drug dealer uses) I ended up being about 15 grams heavier on the port-side carb. This turned out to be even worse when I made the newbies mistake of changing the scale display from metric grams to Whitworth grams!
So - would you recommend:
A: Try to shave a bit more of the Starboard side carb with the un-precise grinder.
(Bearing in mind that my grinder is from from Super-Cheep Autos, the ones which you can't change the disk on, and its getting a tad blunt).
B: Gluing lead weights or similar to the Port carb at a point that would also have the advantage of balancing the centre of mass (and hence centre of inertia) of the carb?
C: Buy one of those flash Ozito grinder from Bunnings and repeating "A".
Thanks in advance.
Dave
P.S. Great job here and well explained, but just couldn't resist this after watching Ichiban Moto's latest release.
lol, lol, lol pmsl
Hey Andy, the XS1100 is magnificent. I’m building up a late CB750 cafe racer at the moment. Planning to fabricate two 2 into 1 cylindrical airboxes with two big K and Ns to try and overcome the CV carb with four pod filter problems. Where did you get the small front mudguard.? I haven’t managed to find anything suitable and thought I might have a go at cutting down the Honda original.
G’day Tim, i bet you’re having a great time with the build, I know I did. I cut down the original, see it here ua-cam.com/video/qwNlQQuE6VQ/v-deo.html thanks for watching
Thanks for that. Reminds me I need to check the UK law before chopping it down. The Honda has a plastic mudguard so I’ll try with the Dremel.
Where in Aus are you located ? Sydney ?
Hobart
I have a question. I have always been the guy who is passionate about mechanics cars bike motorcycles ever since i was a kid cuz we couldnt pay to have out stuff fixed but i learn as i go so im facing my fear of carbs today. I bought a project bike that looks much like yours a week ago. Its a 1982 xj11 i put a new engine in it got it all set up fired it up and it is revving at about 7000 rpms. I checked the idle screw and it wasnt even touching anything. Not completely knowing its purpose i looked up online where to set it i screwed it all the way in backed it out a half turn. Didnt help at all. I thought vaccume leak of some sort so i sprayed around with some starter fluid no leaks engine just roaring. I figure the carbs were "jetted" for air stacks and straight pipes. But the butterfly valves are shut or appear to be via idle screw fully loose. The engine ran fine when i bought it but the transmission was bad I got a deal for a whole new engine. I have to theories. The engine i pulled was modified idk how and set up for more fuel and carbs need adjusted or a vaccum leak i can not find. Its a month wait on the only guy in town doing carb work so i am just gonna figure it out. Now my question there is the idle screw you talk about at 9:01 but are there individual scews on each carb i think they adjust idle via the air fuel mix idk. Is that how i adjust the carbs? They have been recently cleaned and synchronized.
G’day mate, sounds like you’re at your wits end. Here’s a few things to look at.
1. If the idle adjustment screw (singular) is not touching anything and is high reving it is possible that your accelerator cable is not adjusted correctly.
2. Yes there will be an air/fuel mixture screw on each carb. Carefully wind them all the way closed and then wind them out two turns.
Start there and see how you go.
Andy's Motorcycle Obsessions i think i was a throttle cable issue it was just a bit bound up got it running today..
Help !!!!!!!!!!
Hey man so I have a question I need your help
So I was riding home one day and I ran out of gas I turn my Petcock switch to reserve then I went to the gas station I didn’t turn the Petcock switch back to the on position The bike is working fine it’s seem to be at least I get back on the freeway and it works fine but ever since then if I try to hold high speed for long periods of time the fight starts to bog and will eventually cut off If I don’t let off if anyone knows anything please let me know it would be a huge help
I have a Suzuki katana 2006 750
That engine sound was amazing - is that normal for this bike or is it how you've got it set up?
They’re somewhat more sedate in standard trim. This bike has extensive cylinder head work, a big bore kit, the RS36 race carbs and four into one with not much muffler.
Sounds super tight. Must be lovely to open it up on the road. Nice work!
Hi Andy,
Bloody brilliant videos. I've got almost all of my XS1100 knowledge from you and Basket Case.
What's the difference in hose and adapter sizes for? I have an '80 xs1100 stock carbs and I'm looking at purchasing the digisync as I've had problems with them. Which would I need?
Many thanks,
Greg
Hi Greg, the adapters are for manifolds with screw in ports. As the XS1100 has tubes mounted in the manifolds you don't need any adapters. You just remove the rubber plug from the manifold and push the hose straight on. Thanks for watching, Andy
Thanks mate!
At 12:00 what was that that you pulled from under the wheel well?
G’day mate, I use a MotoGadget M-Lock ignition. It uses a RF reader to switch on and off. I was waving the fob past the reader, which is located below the seat, and I placed the fob on the lift.
motogadget.com/shop/en/m-lock-rfid-zundschloss.html
@@ANDY5 That's what I thought it might be. I'm sold. Ty.
Andy i need your help,
I have a 1978 xs 1100 ,i took off the airbox and fitted 4 k&n filters
Ran ok ,BUT now when the bike runs i have petrol pumping out of the airtubes that where connected to the airbox.
I cleaned completely the carbs ,but petrol still pumps out!!!!!
I cant think of anything it could be ,any ideas????
Thanks in advance ,ride safe !!!!
Cheers mate !!!!!, bye
G'day Andrew. The factory carbs run far better with a shared air plenum, a lot of engineering went into that airbox. That being said it shouldn't be doing what you're describing. The short answer is that they are flooding, those airtubes are the float bowl breathers. The task for you now is to work out why. It will be fuel bypassing the needle and seat and it could be for a number of reasons. It could be that the needle and seats leak. It could be that your float level is set too high, it could be that one or more of the floats are being impeded by something within the bowl and are unable to operate properly and close the needle and seat. Watch my video on bench tuning a set of CV carbs from a GS1000, the process is the same. ua-cam.com/video/8p7s6U9HMoE/v-deo.html
@@ANDY5 ,thanks for the immediate answer
Will watchsaid video ,go through the process, and report back
Take care
See you on the road (huh, your in tasmania and im in france!!! ,you know what i mean)
Cheers again ,bye
Is that a 750 k motor?
450K
Im look for a tune.. adjustment..
First of all my bike is really old.... so There is some sett off.
2nd of all. The bike was Made for leed gas.. back in 1996. And NO ethonal...
Thats the perfect tune.........
For last 13 years we have here in sweden 5 % ethanol okey fine thats not match.....
That Will be Lean by just a snitch....
But son this year 2021 it Will be 10% of ethanol! Thats really alot..
Well usa have That for long time but not me in sweden.......
How do i do whats needs to do ?
Now When they put 10%....
Do i need to adjust the needel? One up or down ?
Do i need some bigger or smaller jets?
Thx , very helpfull
My bike only runs with starting fluid and it revs up to 6k when I start it n don’t touch the throttle. My carb boots look a lil cracked but not on the inside so idk
I would suggest that it isn't getting any fuel, blocked jets would be my first guess.
I thought the same. I’ve been around bikes atvs through my childhood n deep cleaned every jet n now won’t start at all so idk. Might send to a shop
Does anyone know if there are any main and pilot fuel jets from other carb manufacturers (ie: Mikuni, Keihin, ect.) that can be substituted for use in the Hitachi HSC 32 CV carbs used on the 80-82 Yamaha XJ650?
Quadflopper101 check out the manual on what size jets came stock and checkout dynojet or other manufacturers for a replacement. Hope this helps
due to a family crises Dynojet is out of my price range right now. because the original stock jets were kinda beat up I replaced them with new stock jets along with all the other parts you normally replace in a rebuild, I even checked to make sure the jets were the actual correct size but bike still running way lean when not on pilot circuit so just to try and get the bike to run richer above 3000 rpm I increased mains all the way up from stock of 110 to 116 which made the bottom end run so rich that it stumbles all over itself but above 4000 rpm's the bike goes dangerously lean equally on all 4 cylinders. Ive been working on bikes for 40 years but don't have much experience with CV carbs, there has to be something I'm missing so I'm hoping someone might have some other ideas beyond the obvious ones. thanks for responding though....
I don't think absolute accuracy is necessary to balance the carbs, only that each input reads the same, or that if there's a variance that you take note of it. You're looking at relative changes, nothing more. I used this and found it worked great: www.carbtune.com/carbdtls.html Much better than that Motion Pro thing that lets all the fluid into your engine if you blip the throttle a little bit too much!
The Motion Pro units are aluminium rods, not liquid. Thanks for watching, Andy
Great info. Thanks!
SUBBED!!!
Need a motometer and a vacuumcleaner ...
👍🏻