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Motorcycle Repair/Slow Jet size for CL77 1967


QUESTION: Hi Bill I have a 1967 CL77 & I am rebuilding the carbs and I have #38's & #40's Slow jets to chose from,  What would you suggest for sea level.  Thanks

ANSWER: John, Honda called for #38 idle jets back in the day, with #130 mains. I have had to increase main jet sizes on the CB77s, due to alcohol fuels these days, but it seemed to affect the main jet sizes more than the idle jetting. Make sure that the carb flanges are flattened out and that you put in fresh o-rings on the insulator and carb flange, so you get a nice air-tight seal to prevent air leaks from altering the jetting calibration. Idle mixture screws should be about 3/4 to 1 turn out when the idle jets are sized correctly. Start with the needle clips in the middle (#3) position, assuming you have the OEM parts. Keyster kit calibrations may be off enough to cause you to make additional changes.

Ignition timing is critical to how the carbs perform, especially at idle, so dial in your spark timing first, then fine-tune the carbs.

Bill Silver

---------- FOLLOW-UP ----------

QUESTION: OK got her up & running and idling like a kitten. rides/drives & accelerates fine.  I have #38 idle jets & #130 mains, fuel air is at 1 turn, no muffler but baffles are in.  

Question is: There is a dead spot if you quickly twist the throttle off idle  & quite a bit of popping on deceleration.  

Do you have any suggestions for fine tuning?


I would raise the needles up a notch and see if that makes it better or worse. It sounds a little bit lean off-idle/mid-range. Did you change all the o-rings on the carburetor flanges and intake manifolds? Any carb flange warpage?

Bear in mind that these carburetors don't have an accelerator pump to help enrich the off-idle mixtures, so there is only so much you can do with these types of carburetors. Make sure your ignition timing is spot-on before you do much with the carbs, though.

Alcohol gas makes them run lean, as well.

Bill Silver

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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