Inside A Motorcycle Carburetor - Idle Circuit | MC Garage
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- Опубліковано 9 кві 2019
- Does your motorcycle idle funky or not at all? There can be several causes for this, but the most common and first thing you should troubleshoot or tune is your carburetor. Today on MC Garage we are going to talk about the idle circuit of a carburetor.
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With modern fuel injection a stable idle, no matter the conditions, is a given, but if you have a carburetor in your ride, things could be less consistent. Environmental factors such as altitude and temperature can require you to make some adjustments to your carb.
And of course the darn thing could just be full of crud from sitting too long or from not being serviced for a long time. Ari did a killer video on how to clean a carb a few years ago, we’ve included the link to learn all the ins and outs of cleaning below. For this video we are continuing on proper adjustments of all the systems of the carburetor.
If you haven’t watched the first two videos in this series of carburetor series, go back and watch them first. Links are of course below.
The pilot jet along with the mixture screw is responsible for how your bike idles. It also provides the fuel for about the first 15 to 20 percent throttle. The pilot jet is the smaller of the two jets under the main body of the carb in which fuel flows to mix and atomize with the incoming air on its way to the cylinder.
In your service manual the manufacturer will list the standard size pilot for your bike as well as give alternatives for ranges of altitudes and temperatures. However you can’t just change the pilot and be ready to rip. You might be close, but there are a few steps for tuning. This is where you are going to need to listen to your bike.
First your bike should be warmed up. When the bike is cold you are going to need to use the choke or enrichment circuit. A cold engine needs a richer (more lower air to fuel ratio) to run. Most flat slides will use a seperate enrichment circuit to supply additional fuel. It’s basically a plunger that opens and closes the circuit. Other carbs use a secondary butterfly to limit the airflow while the pilot provides the same metering of fuel, thereby creating that richer mixture. Once the engine is up to temp, turn off the choke.
We also need to be sure your air or fuel mixture screw is in the middle of the range to start this process. If the mixture screw is on the airbox side it’s an air screw. This one meters air into the pilot circuit. Turning it clockwise closes the opening, richening the mixture. Counterclockwise adds air and leans the mixture. Check your service manual, but a proper baseline setting should be around 2.5 turns out (clockwise) from fully closed or seated.
If the mixture screw is on the engine side, it meters fuel instead of air. Clockwise is less fuel and a leaner mixture, whereas counterclockwise is more fuel for a richer mixture. Just like the air screw, check your manual for the standard position or starting point, but a good rule of thumb is this should be around 1.5 turns out. So once you have those in a correct starting position we get down to tuning or jetting.
Let’s discuss what the idle behavior will be like when a warmed-up bike is properly jetted, too rich, and too lean. A proper idle should be consistent without any input from the throttle. It should also settle quickly after revving the engine.
If it’s too lean, you’ll find a hesitation or bog right off idle when you crack the throttle. Also, when revving the engine, the rpm will hang at a higher level than normal idle or will not settle into a consistent idle quickly.
A too-rich pilot setting will give you a sputter when the throttle is cracked. Response will just feel a bit heavy or sluggish. When the engine is revved, the rpm will drop quickly and dip below ideal idle before recovering; sometimes it will just die.
Full story here: www.motorcyclistonline.com/in...
But that’s the basics and will get most of you with a single carburetor well on your way to fine-tuning your motorcycle idle circuit. In the next video we will move on to the needle jet and needle.
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I’m always amazed a carburetor works at all.
You’re carburetor videos have been very helpful when it comes to tuning and fixing my moped thanks man you’re definitely an angel to society
Great tips!...my bike is idling on the high side, so perfect timing with this vid.
This video is among the most helpful explainations on the internet.
This is an absolutely well explained video about carbs. I own a 1994 Suzuki RF600R and just from this video alone I've discovered my bike is running too rich! Exactly like he said, the bike would rev up normally but dip way below the normal idle. It's gonna take a day or too to get it right. Thank you Justin and MC Garage! You guys are life savers.
Ayeee, I had a 04 gsxr 600 swapped RF600
Thank you. I was missing the bit on how rich and lean feel like. Good and simple explanation
Great content and good presentation. But..miss you Ari Henning.
Ari's awesome! Miss him too!
@shroomingnewman 3 I not sure if he resigned or retired. Maybe he decided on doing other stuff. He sent his farewell remarks though.
Mine seems to be too rich, like you said, it's slugish and then it dips bellow idle, it does turn off some times.
Ugh.
Thanks for the video, amazing info.
Great info. Keep up the good work!
Well done - clear explained!
in india usually lower segment bikes till 200 cc uses Carburator and some higher uptill 500cc too and i own a 125 cc Scooter which has the carburator with Electronic choke. Tuning that At the beginner level(me) was not perfect and i learned a lot. seeing this video i can compare and revise the procedure to get better understanding of the sound the engine produces. My other 110 CC scooter had a traditional, no electronic nonsense Carburator which in recent month giving me a problem where its overflow oriface at top and bottom one completely ejecting fuel whenever the engine is cranked. thats problem was a nightmare to solve untill i got a float needle valve to replace with the old one and the problem stopped. thats how amazing and nightmarish the Carburators are. Thanks for the Content.
The best info videos on motorcycle,please make a video on throttle body cleaning on cbr
Finally! Well done
Justin looks like the middle of a "On a scale of Ari Henning to Lemmy from Revzilla"
Thanks for the examples. Although I didn't really hear a sputter in the rich video.
I have been waiting for this video since 1885
Greetings, my sir from Indonesia👍
i like how you explained the tuning of the carbs by listening to the bike. but how does it work with 4 carbs on an inline 4 engine? i mean, when 3 carbs are perfectly tuned, but one is slightly or a bit more than slightly off, will i be able to hear it?
i also wouldnt mind a more complex explanation of the system, the cycles etc, maybe even by using some sketches on a whiteboard like some other channels do ;)
anyways, keep up the good work
You'd need to do an idle drop. Instead of listening, you use the tach to watch the rpms as you make adjustments. Turn them all out a quarter turn in sequence until the rpms stop rising. Then tighten the first screw until you see a 50 rpm drop. Go back out a quarter turn, then move on to the second screw. It's tricky but satisfying
Great video. Who tosses their carb into the air?
my two stroke ke100 idles fine possibly on the rich side. It doesn't really bog in neutral. It only bogs under load if I open the throttle more than 50% . If i gradually open it its fine.
Thanks. Great series. But can you drop the disco beat?
hi thanks for the explanation. ive just changed my pilot jet and main jet .the fuel screws have been adjusted and are in the same position as before. is that ok 🤔i set the fuel screws that gave the fastest idle .
What is the best carburetor for a venom x22 2020? I have a hole in my airflow box and it's a brand new bike. So I'm doing repairs and replacement. The hose is going from the carburetor to the airflow box. I also need to know the best hose to use. Let me know. Thanks
I have a 2004 triumph speedmaster 790 that I ride regularly but it stumbles at 70mph+ in a strong headwind, like it may be lean. It has airbox/air injection delete and k&n filters.
Will you post some video of how to tune multi-cylinnder carburetors?
To get each carby synchronised with each other (all opening at the same time), remove the air filter and use a length of tubing with one end near your ear and the other end just inside of the carby while it's idling and listen to the air being sucked in, then compare with each other and adjust linkages so all have the same suction noise.
Carburetor are a work of art and I'm loving to work with it as it is simple and no electronics failure will happen to this bad boy. If you want more power from your bike just slap on a bigger carburetor with the right jetting and your bike are already good to go. Fuel injection on the other hand need a Dyno tuning which never be good on your wallet and all the upgrade parts are expensive as hell.
Hi, I have both a Intruder VS1400 and Marauder vz800,,,I have the bikes running well and synced and carbs inspected and set to spec,,,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 know this is a long shot because this is a couple year old video. But I put a new carburetor on my motorcycle. Is it already free tunes for the carburetor or will I have to tune it myself. Maybe a dumb question. But I have to ask.old carb was leaking
can anyone tell me the functions that those plastic tubes (the clear ones that connect to the carburetor) . Thank You
Hi, my throttle is always sticking at full throttle everytime, is that because the needle in the carburettor isn't in the right position? (Its also a 2 stroke )
I need a video or diagram on what the other knobs and stuff are like on the top of the carb above the intake port
Hi i have a tgb target 525 . 503 cc engine. This use a mikuni carb BSR 33 (33MM DIAMETER) and i wanna ask what is the best jet combination to get max power and high rpm( 9.000...10.000rpm) at the moment is runing a ignitech cdi unit witch is probramable and no rev limited. From the factory this came with .225 PILOT JET and 145 MAIN JET .Thank you
Was there any difference in the lean and rich examples at 3:30-ish? Sounded the same to me.
What if the carb doesn't have fuel and air mixture screw, how do you tune this carb? I ask because where my fuel screw should have been there was none
I’d check for vacuum leaks before pulling the carb.
I have a 1975 Honda mt125 elsienor It bogs a little in the first 1/4 throttle but up on the top it rips and I am making it a cr125 but how do I fix it.¿
Hii, I have ninja 400,
My bike used to run very smooth and goes easily up to 140-150 without much vibrations. But sometimes it is hard to go even 120 the bike start shaking and vibrating. If I am lucky the bike suddenly starts to run smooth and feels more power but sometime if looses power. And I can hear some sort of light noise coming from the engine area it’s like a small leak from exhaust but there is no leak it comes under the engine area. Do you know what could be the issue and what I can try?
Videos about F-CR Carb´s please!!!!
Thanks and keep going with good work!!
Are some air screws covered by the manufacturer? I pulled out a screw from the exterior of my carb on the engine side and it had a pointed tip, I believe it is the fuel screw, but there are some spots that look potentially like a covered screw on the air side, but there is nothing else on the exterior of the carb that I can adjust.
Yes, carbs sold in the US often have plugged or non-modifiable ports/screws/etc. For instance, my '95 XV250 have a brass plug with a tiny hole drilled in it instead of a pilot screw.
well for me, the bike turns off when opening the throttle wide even if it's in gear .. does that mean the mixture is rich ?
Hello, i have a kawasaki ninja 500 and The bike was not started în The last 2 yeas. 3 days agoo i decided to start it. I puted a new battery, puted fresh gas and it started easy and the engine runed for about 30-40 second. It stoped and i noticed that the carburetors were fluded bad, liking from the air filtre. I decided to take the carbs off, opened them, cleaned them, maked the flote work again and now after i asambled The carbs and puted them back on the engine, the engine dus not start, it detonates in the carbs. Dus not start whit start spray, The Last detonation was s-o hard that it threw away the carbs from the engine whit a lil flame. I hawe spark on the coil, i have gas suked in to the engine, i have good compression, what could be the problem?
ok so i have a question. I got a 250cc 2 cilinders and 2 carbs. And why does it seed in the "manual" that i need to turn carb no.1: 2.5 turns and carb no.2: 1.5 turns?
The manual is a old copy and do not know if it is the original bit the the bike is a 74".
And no aftermarket filter or tuning all is stock. And its 2 stroke
This is common for V configuration engines. Usually the cylinder in the back gets a slightly richer tuning, than the front cylinder. That's due to the higher temperatures of the rear cylinder because it doesn't get as much cooling as the cylinder in front.
@@Chris675R but i do not have a V engine. I have a inline 2 engine.
The bike is a moto guzzi ts 250.
i'm hoping that the mixtures are right i do not want to destroy the engine.
How do I adjust the carburetor for high altitude roads?
Higher altitude means the air is thinner. If you go from low to high altitude. The bike will run richer than normal. So you need to lesser the fuel intake. That will normalise the engine.
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No links found in the description 🤔🤔🤔
Updated
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Anyone ever used the self adjusting carbs? I've always been intrigued, but never wants to drop the money on them.
Is it the same to use the choke to start a cold engine as is to keep open the throttle for a while? (Same revs sound for the same time)
It is not. The choke either restricts airflow upstream the butterfly/throttle piston to create additional suction that draws more fuel into the carb throat, OR flipping the choke activates an entirely separate "enrichener" circuit that feeds more fuel through dedicated passages. In both scenarios, the choke supplies additional fuel into the existing closed-throttle airflow to enrichen the mixture.
@@AriH211 So using the choke would be finally more efficient to start a cold engine and heat it up. Thank you for your reply!
@@aricafoix Yup. That's what it's there for!
Great info.
I had a hard time watching the video, because I was focused on the shadows from your glasses on your face. Maybe change the angle of the lights
Christ Tom you must be a hard man to please... "Yeah honey, you were hot an all, but unfortunately the shadows your thighs made when you were riding me looked a bit like Paul McCartney's face. Not all the time honey, I don't want you to get a complex, but, you know, some of the time"....
Unsubscribe brother, this channel sucks now
Will lean mix damage the engine?
3rd out of 5 carb vids
Which jet do you change? Idle jet?
What could be the issue when the carburettor dumps fuel (in the intake) when the bike is off? After many tries to start it, when the fuel evaporates it runs fine. It has an automatic, electronic choke.
The floatvalve isnt sealing if gas flows to the intake on its own.
@@JensEskildsen The bike runs totally fine when it's warmed up. Could adjusting the float height be the solution?
@@socas_nic Check if float is not cracked or punctured, doesnt take in gas and if it operates freely. Also would be good idea to replace float needle valve.
@@socas_nic A slight chance yeah, but I'd change the floatvalve for sure when youre in there.
Check your float valve. Sometimes it's misaligned or the rubber seal has worn out and need to be replace.
didnt you say the baseline settings backwards it 1.5 for air and 2.0 for fuel
Heyy. I love mc garage. Was off for some time. Can anyone tell me. Wheres ari?
Zack and I are both making videos for Motor Trend now. You can see our shows (Throttle Out, Throttle Out Garage, and Throttle Out Commute) at motortrend.com/moto.
@@AriH211 thx for answer. Cheers m8
My engine runs fine in idle when first fired up, though after the engine warms up it starts to race. I have adjusted the carburettor idle throttle bolt loosened all the way off and it still continues to race. I have noticed that when this occurs and I put the bike in gear and ride the clutch a bit whilst remaining stationary the idle then drops again, though increases again when back into neutral. Has anyone got any idea what may be causing this?
Airleak on the intake side?
@@MaaZeus Already checked all of that. I have since done a more thorough check of the carburettors using a carburettor gauge test kit and discovered that two of the four carburettors were completely out of synchronisation and when the engine warmed up the synchronisation became more unstable causing the engine to race. Now that I have synchronised the carburettors the engine runs better than ever.
SOMEONE PLEASE ANSWER....!!
My motorcycle's RPM increases when it is kept for a minute to arround 2k RPM from 1.4K...and after riding it for 4-5 mins it's idle RPM reaches to 3 - 3.5k RPM....there is no problem for throttle cable....
The motorcycle is a japanese machine of 150CC....(Honda Unicorn)
Due to this problem the mileage has reduced.
Did not inspected the choke wire...A mechanic said the carburetor need to be changed...because the mixing screws are jammed...
WHAT TO DO???
Check the choke, if it's on or stuck that will cause exactly what you describe. And find another mechanic who's not out to sell you a carb.
@@triumphrider9796 let me check...Thanks anyways
hard to have a warm bike if it wont start
Engine side would be what side exactly seeing I see the engine from both sides
Why does a carb only have idle mixture screw? Its a CVK
Rev-Idle Sounds
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Hi my moterbike dont like the rain when I was ridding to the shop and back home it was working as soon it started poring it down it dont like the rain. There is oil petrol in the moterbike new battery in it only works when its dry do you know why this happen' s to me can you do a vid for me please or message me on Facebook hope all well stay safe
( Pricey Photography )
Why does cold engine require richer mixture?
Because when an engine is cold, so is the air, and when air is cold there is more air therefore needing more fuel in order to start up
@@aussieguy1593 by "more air" you mean denser air?
Ivan Arifin exactly
@@aussieguy1593 There's also the fact that the engine (intake tract, piston crown, combustion chamber, cylinder walls, etc) are cool and therefore the fuel is less likely to vaporize and may even condense on surfaces. The solution is to supply more fuel to ensure sufficient combustion until the engine warms up.
Bring back Henning
Ravi Kumar unsubscribe brother, I'm about to, this channel sucks now
Both of you get the *FUCK* out lol
What is the value of the idle RPM of any bike? Is it 1100 RPM? My bike's needle drops below idle 1100 RPM but it automatically shuts down at 500 RPM if I rotate the screw and bring the needle at 500 RPM. What RPM value should the bike automatically shut down when it is in neutral or within how much time and RPM value should the bike automatically shut down in neutral? Please show the screw turns of resetting idle mixture of carburettor.
900-1000 rpm is optimal, but if she runs rough or stalls at those speeds, 1100 is fine
@@tentacleslap5531 My another question is what RPM value should the bike shut down if we decrease the RPM needle by turning screw? My bike shuts down at 500 RPM if I bring the needle down at 500 RPM but previously it used to shut down when the needle comes at 800 RPM.
@@nathanielpeter3296 It doesn't really matter. Pretty much anything will stall at 500 rpm
@@tentacleslap5531 Ok.
Carburettors? Okay I agree quite a lot of motorcyclists want to know about them and use them, which even includes me, but even this large group is tiny compared to the vast majority of bikers who are all on fuel injection nowadays.. let's talk about that guys, carb videos can be an additional bonus but don't focus on it at the very first instant..
480p
Are you fuc***g kidding me
Dude, you look and move like an animated South Park character. It's uncanny.
Yeah, I'll stick to fuel injected bikes.
His prompter is below the camera which makes him look lazy when speaking
Hrishikesh Sabde it's time to unsubscribe brother, this channel sucks now
make an video for inline 4 carns
You mean *carbs??
Its the same principle, just multiplied by 4, and you need to syncronize them. Theres plenty of videos of that.
Mehh
oh
First
Carb. are deads
Can't stand this guy. In addition he sounds and acts bored. Seems like he sees this content as work and not as his love
Yup: they were like "quick get a frumpy guy with a beard to read the cue cards, that'll be relatable to the viewers " 😐😒
Unsubscribe brother, it's what I'm about to do: their little moderator is threatening to ban people if they give any criticism; this channel has lost its way
We want ari Henning as host not this old uncle
I don't see you producing content. Justin's doing a great job; screw off.
Justin Dawes your content is slacking and you're threatening to ban a viewer? 🤔 Please don't stress yourself, I'll start by hitting the unsubscribe 🙄🖕
Unsubscribe brother it's what I'm about to do: check out motorcycleMD he's legit