The Cure For The Cold-Blooded Carbureted Motorcycle!
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- Опубліковано 14 чер 2024
- EPA mandated, lean carburetor jetting has really caused headaches for motorcycle riders from the late 1970s through the early 2000s! Extended warmup times, surging, stalling if you pull away too soon after startup, poor running at low throttle settings, etc., can all be symptoms of lean factory jetting of your carbureted motorcycle. This problem exists on every brand of motorcycle and can be more pronounced on different models within the brand lineup. Fortunately, there is an inexpensive cure for the cold-blooded motorcycle! In this video, I will discuss three different classic motorcycles that all exhibit symptoms of lean factory jetting and the changes I made to cure them (including specific jet sizes for each bike). Please note - these changes work well for my specific elevation and climate (Pennsylvania) - elevation and temperature impact jetting! All of these bikes are running the stock exhaust and airbox. All air-fuel screws are turned out around 3 turns.
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Wow Jon,,,,,,,,, the Honda CB400 Hawk...... When I was just 16, got in a fight with my folks, got kicked out of the house, so I went down to the Bay Area (of the SF Area). Lived with my oldest brother, then oldest sister, and working while going to H.S......... While speaking w/ my brother, explaining to him how I wanted to buy a motorcycle. A friend of mine had one for sale, a 78 Honda CB200. After speaking w/ my big bro about it he told me "NO" , "NO WAY"! I couldn't understand why he was so stern about that? Well, he explained to me, "Cel, if you get a little 200 cc bike, in 2 weeks after owning it you're gonna want MORE POWER". Well so I began researching motorcycles, and first bikes. (the early '80's) mind you. SO, I was thinking of a "Mid-sized" bike, and "THIS" was what I was planning on getting . A brand new: Honda CB400 Hawk. The CB400F finished up in '77, so that was off of the table. Long story short, went back to live with my folks, finished H.S. where I should have. I , after H.S. immediately moved back to the SF Bay area, and began to enter College, and bought my first bike a 1981 CX500 Custom.
Great story and it ended with you getting a bike.
Hell yah dude! the CX500 is such an amazing bike for its time. Would love to get my hands on a GL650 if memory serves. Stick with my 82 cb650sc for now. She'll get friends eventually lol
That's so cool! Thanks for sharing the memories. Cheers!
That's funny, At 17 I got a Honda CM 450 custom as my first street bike, basically the same engine in the Hawk and the predecessor nighthawk 450. Then with in a year got in a fight and kicked out. Well they said just leave like hundreds of times before, that time I followed through. That bike got me around during a lot of BS. Still fond memories
@@plap. Yeap, I'm with ya!
Some things don't change. My 2019 Indian FTR 1200 (base) is so cold blooded I swear it has carbs. for the same reasons. EPA regs. The difference is I would have to spend about $400 on a gizmo and new map not $10 on jets. That's what I call progress. It would be interesting to put a set of flat-slide carbs on that engine. I bet I could get it to run just as good. Get rid of all the electronic this and that and gain long term reliability. But the Government would be pissed !
Yep. Cold-blooded FI bikes are a real problem as well and a much more expensive fix. I laugh when people act like FI is the answer to all fueling issues. I've owned too many fuel-injected motorcycles and know better. Thanks for bringing up the FI point. Cheers!
Good morning Jon. I have the house to myself today. While making my coffee, my mind immediately went to, "I wonder what Jon is going to talk about today" 😉 ☕️
It's cool how you "know" your bikes and make improvements.
Eric in NC
Thanks, Eric!
Sometimes, when CV carbs hesitate, all that is necessary is a shim under the needle, and like a previous comment said, pull the mixture screw covers and adjust factory settings a little richer. Obviously the big 1100 was cold and lean back then, and needed more petrol. Either way Jon, thanks for another informative trip inside our classic bike world. Nice 400 Hawk , I had a black one. And also, extra clean GS1100E. That was a FAST bike, with fantastic low end grunt.
Always good info. - KK
Right on! I had shimmed the needles and richened the air-fuel screws on the Hawk already. It was evidently quite lean from the factory. I'm not surprised since I had to richen jets in my 1979 CB750K and all my CB900Cs as well. Cheers!
Ive been tuning carbureted dirtbikes for years, going up one on the pilot jet is almost always the right move. I just took my first stab at tuning a 79’ kz650sr that i bought, did the same thing, and it seems like the jump from a 15 to 17.5 pilot helped alot but could maybe still be even better with a 20. Ive gone through every system on the bike and am confident in their condition. Something ive begun to consider is lean jetting for 1979 gasoline is not the same as lean jetting on 2024 california ethanol heavy gasoline. Ethanol likes rich jets
Right on! The lean pilots are usually the culprit causing noticeable symptoms in the 0 to 1/4 throttle range. The mains also benefit from a one size bump in many cases (as the roll-on testing in this video confirmed). Cheers!
Don't forget to open up the pilot air screws. It helps alot.
@@CountCraigula Already done 😉!
Good point! I just drilled out the plugs and adjusted the mixture screws on the carbs on most of my bikes and it helped quite a bit.
Right on! I had shimmed the needles and richened the air-fuel screws on the Hawk already. It was evidently quite lean from the factory. I'm not surprised since I had to richen jets in my 1979 CB750K and all my CB900Cs as well. Cheers!
Jon your show makes me want to ride my bike , even though it's over 100F, each day here, in Yuma, Az
That's toasty!
Nice bikes Jon !
At 68, you bring back memories.
Regards.
Trinidad & Tobago.
West Indies.
Thanks, Ramish!
I was worried i had some engine issues with cold start sounding kinda lumpy. Glad its just a vintage bike thing. Love my 82 cb650 nighthawk. You put out a lot of good videos. Thank you
Thanks!
Over the years I have also found that removing the plugs that block off the pilot air screws and adjusting them richer (equally of course) helps tremendously.
Right on. That was already done on these bikes. Three turns out usually does the trick. Cheers!
That GS1100 is a beautiful machine! Lovely area where you live as well.
Thanks! Pennsylvania is a beautiful area to ride in. Cheers!
Kaplan Cycles in Vernon,CT does the thing. Kaplan Mechanics on all classic motorcycles are completely gone through,and the carbs are re-jetted . In my opinion
The emissions standards weren't necessary.
I understand the emissions standards from a pollution standpoint, but it did make life less pleasant for the end users. Thankfully, it's a curable problem. Cheers!
Thanks for another very helpful vid, Jon. I like how you keep your bikes mostly stock but make useful tweaks. These bikes were sold with certain compromises to sell at a price point, emission or noise standards which leaves room for improvement. Especially some of the more popular models with a fan base, stuff is available in the aftermarket. I can't leave my old bikes alone, usually starts with the brakes. I find it rewarding making them the best they can be...
Right on! Safety is paramount, and a set of steel-braided lines goes a long way. And, like you, I want them to be the best they can be. Cheers!
Enjoyed the video, Jon. Going to give the carbs on my VMAX some attention. RIDE SAFE OUT THERE!
Thanks, Henry!
Agree with you on this. I did this on my 1980 CB650 and on that bike Honda really tried to make messing with them difficult. In addition to the small cap over the mixture screw they added (Keihin, actually) press in pilot jets, which they now make replacements for, thank goodness!
Press-in pilots (and the Keihin carbs themselves) were not my favorite. There are so many more parts than the Mikunis. I had to richen jets in my 1979 CB750K and all my CB900Cs as well. Cheers!
I've still not owned anything with fuel injection, I've been riding bikes for 50 years.
Luckily in the uk, we didn't have the problems you had over there.
But even so a Dynojet kit always helped the engines running.
My latest bikes are a streetfighter blackbird and a st1100 pan european.
Plus my 45 years old Beamish Suzuki trials bike.
Right on! Often times, just going to Euro-spec jets does the trick. And as you said, a Dynojet kit is definitely an improvement. Cheers!
I can appreciate these old bikes a lot. But those carbs are always annoying. I love the 90s bikes the most with injection. Those where great times. Simple but very reliable bikes.
Right on! Though not all FI systems fuel that well, and it's common to have similar symptoms on the newer bikes. To cure an FI bike, you'll need to spend money on a tune. Cheers!
A year later, after going through some college, (and working a HONDA DEALER) found/ bought a beautiful '75 Honda CB400F. Well, I've owned it for now some 42 years...... (sold the CX500C after putting on nearly 50K).
The CB400F is definitely a keeper!
Great informative video as always 👍👍
Thank you!
Great clip! Thanks...
You're welcome!
Excellent and informative Video..thank you
Thank you, and you're welcome!
this is an inspirational one; thanks!!
You're welcome!
Great tips ❤❤❤
👍🏻
Great touring bike If it was mine I would put a quarter fairing on it and find one that looked good , wind blast on your chest for hours increases fatigue and every standard I have had I put one on even if it was a cheap EMGO .
I agree. I've put fairings on many bikes, and they make a big difference at speed.
wow did not know that older bikes so lean explains why choke dumped so much fuel just to start ...- new bikes fuel injection is opposite all rich and exhaust for regulation - ECU flash and let it breath runs crisp better up HP - great content love the classic bikes with carbs got a different feel /have you ridden a 2 stroke 250- cr 500 dirt bike ?? got to ride one for rush power to weight on dirt or Trails ect... or super moto type great ! fun cheers
Thanks, Douglas! I would love to ride a 250-500cc two-stroke if I get the chance. Cheers!
Great tip.
Thanks!
My first bike was identical to that silver CB400T Hawk. I wish I would have kept that bike.
This one is for sale... 4k original miles... Lancaster, PA.
Another issue that many people don’t realize is the fact that these classic carbureted bikes were never designed to run on ethanol fuels such as e10 or e15. Ethanol fuel will noticeably lean out your mixture and create drivability issues. Use a good 89 octane non-ethanol fuel exclusively. On top of that ethanol fuels wreak havoc on carburetor and petcock seals and gaskets.
Right on!
Old bike hesitancy at low RPM is more commonly due to leaking manifolds or vacuum tubing.
You need to test at WOT to determine if your main/pilots jets are undersized.
You are correct that vacuum leaks can cause running issues. Changing jets will only work if ALL other systems are functioning properly. At WOT, only the mains are at play. I tested both the XS1100 and GS1100E featured in this video at WOT 40-80 and they both significantly improved. The idle circuit is only in play between 0 - 1/4 throttle settings. This is the off-to-on throttle response and steady-state cruising and low throttle settings. All three bikes were improved in this area after the changes were made. Cheers!
@@jonsmotorcyclerescueandrev3538 To unpack this a little, pilots can only be correctly be sized after the mains.
In my experience, most old 70's/80's bikes are slightly rich jetted. but blocked jets, carburettor passages, leaking valves, rings and manifolds work against a crisp response at low RPM.
Gunson colortune plug is helpful for pilots.
Great bikes. I still have a Blue 83 GS 1100E with blacked out components like yours. Also had a Honda CM 450 custom which basically had the same engine as Your Hawk and its predecessor Nighthawk 450. My bike after the CM was a 88 Hawk 647GT Interesting similarities i thought
Nice! I recently reviewed the Hawk 650 GT. It's also a fun, great-handling machine. Cheers!
@@jonsmotorcyclerescueandrev3538 ELF single sided swing arm, light and great handling with aluminum twin spar frame. Ahead of it's time. Had a lot of character especially with the Muzzy pipe mine had. Still one of my favorite bikes.
@@plap. Right on!
Sweet bike’s, love that GS ,
Right on, thanks!
Hi Jon as always I learn something new from you , thank you here in California the gas contains ethanol would that will contribute the cold blooded on the bikes??
We have the ethanol gas here, too. It doesn't help them run better but shouldn't contribute to the cold-blooded symptoms.
Not sure if it has been covered already. My first road bike was a 80 Suzuki 450. Had the same problem, but I fixed mine by placing a small spacer under the needle clip. Kind of sleazy, but it worked.
Right on! I have used that method too, and it works on some bikes. I had shimmed the needles on the Honda in this video, but it wasn't enough. Cheers!
Had the same color 83 gs1100e when it came out,the anti dive on the forks is dangerous when hitting stutter bumps,still have a mint Bassani 4/1 pipe for it in the garage,had it for a year & traded it in for a 84 Fj1100 which I still have in the garage along with a busa & a 14r,also had the xs1100 u have,funny I went to the HD dealer for a chrome bolt for my sportster & seen the xs1100 ,I asked for a test ride & traded the sportster in for the xs1100
Very cool, Joe! I actually dropped a GS1150ES because of the anti-dive on stutter bumps. I have a beautiful 1986 FJ1200 in the garage as well. They're great bikes. Cheers!
@@jonsmotorcyclerescueandrev3538 my gs1100 lost a piston wrist pin right after I got it,so under warranty it got fixed,it ruined the cylinder sleeve,I also went down on it on stutter bumps,the anti dive is dangerous ,it doesnt know the diff. between stuuter bumps & braking,the bars shook so bad I couldnt hold onto the bars & went down ,luckily I beat out cars at the previous light had I not ,probably a car would of hit me,tore up my palms pretty bad & felt time stand still,felt like I was rolling for a long time ,something u dont forget,surprised no law suits
It's no fun trying to ride a cold stumbling bike that's lurching around. In about 4 blocks my lean bikes are pretty good, the another 4 blocks and they're ok.
Yep!
I'm considering the purchase of a modern classic, a first gen FZ1 (2001-5) for my fleet. Most of my more recent bikes have been fuel injected so I've long since left carb issues behind. But the first gen FZ1 is/was/remains such a great bike and so damn affordable and practical now; sadly, it too suffers from OE improper jetting. I'm not capable of carb work so it means I'd have to find someone local and competent to do the work.
I've had several first-gen FZ1s. They had excellent carburation from stock, so you shouldn't need to do anything but clean the carbs if it wasn't modified. They're great bikes. Cheers!
I had an '82 GS750E and the jets were pressed in.
The air-fuel mixture screws had a pressed in cover that needs to be drilled out and removed. However, the jets themselves shouldn't have been pressed in. I also had a 1982 GS750E and they have the standard pilots and mains from factory - both removed with a flat-head screw driver. Yours may have been stripped by a previous owner or stuck with varnished gas (as mine were) - but they're removable. I hope that helps. Cheers!
Hola Jhon.ese problema que hablas es cuando la temperatura ambiente es muy fria? Saludos .excelente
Hola Ricardo! Esa es una gran pregunta. En los modelos estadounidenses, los problemas pueden ocurrir incluso a temperaturas normales, no sólo cuando hace mucho frío. ¡Salud!
I watch Kaplan America on UA-cam and after a classic bike goes through his shop his carb specialist always micro drills the pilot jets. I would love to know the exact process... Increasing the size of the pilot jets would get the same result I believe but may not be exact due to the manufacturing variance in making the jets. Any feedback appreciated.
Micro drilling is the cheap wat to do the same thing. Unfortunately, you're screwing the next guy because the jets are no longer marked correctly. I've dealt with improperly drilled pilots causing horrible running issues. It took forever to diagnose the problem because it had the stock jet sizes in the bike.
Thanks for the video. Are any for sale?
Thanks! Both the Hawk 400 and XS1100 are currently for sale. If you're seriously interested in either, please contact me at jonsmotorcycle@hotmail.com
Cheers!
Nice nice bikes Jon,
Off topic would you be willing to sell that 78 ltd paint from over a year ago! If you still have it.
It's a GM color that I used - I just picked out a paint chip at the body shop that painted it. I don't have any of the paint, and I don't know the number that was used, unfortunately 😕.
The EPA marked the rise of ECO Facism. Its now killing off our beloved motorcycles, R1 etc.
So, where do you find the jets? I have a 2000 CMX250C Honda that takes about 5 minutes of running before it smooths out. BTW this scooter has less than 500 miles on it to date. A real barn find. 😊
Hey John I have a 1979 cb750k with stock jets it also has a kerker header on it I know it needs to be rejetted any ideas any help would be greatly appreciated
I'm sure it will benefit from rejetting. Are you still running the stock airbox? If so, two sizes up on pilots and mains would be a good starting point.
Nice work.
Thanks!
Where does he get parts for these? I have an 78 Suzuki 750, 82, and an 80 Yamaha 1100 that I can’t even get the correct petcocks for.
Finding parts is part of classic bike ownership. I spend hours at times just looking for parts. www.partzilla.com is a great resource for finding parts and part numbers. If the part you're looking for is unavailable through them, at least you can search online by the part number. I hope that helps. Cheers!
🏍👍👍👍
How has doing this effected the mpg on them?
Great question, David. There is minimal difference in mpg. My wrist angle has much more impact on that 😉! Cheers
Side gap your spark plugs. A world of difference.
Side gap ??
@@propdoctor21564 ua-cam.com/users/shorts3OYe7pV0SpI
@@propdoctor21564 The difference is impressive on carburated bikes. Cold start times are cut in half and overall engine running is smoother and a smidge more power. The downside is that the plugs wear on one side more than the other and that cuts it´s useful life to about 2/3 of a standard but it is of no consequence as the benefits are well worth it. In the video you can see the reason why, very consistent sparks generation. It is a little known racer mod. EDIT: They did not allow me to post the video link.
I haven't heard of side gapping plugs before. Regardless, it may give a stronger spark (a definite benefit on older bikes) but won't cure lean carb jetting. Cheers!
@@jonsmotorcyclerescueandrev3538 Of course, lean is lean. Nevertheless try side gapping with some old plugs and feel and hear the difference. It gives older carburated bikes an extra touch of smoothness which is always appreciated. Cheers Jon.
Beautiful❤❤Beautiful❤❤Beautiful❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤Aamir Malik from pakistan
Thanks, Aamir!