• Enter the March CB750 Supply gift certificate giveaway! It's easy... Click here, post something, and you're entered into the drawing!

What does this sound like?

jimminy

CB750 Enthusiast
Messages
77
Reaction score
0
Points
6
Location
los angeles, ca
Maybe someone knows what this is.

When the engine is cold, and for the first 10 minutes or so of driving, the engine steps down to idle just fine when I stop. But after the engine starts to warm up it doesn't want to drop into idle and will rev to around 3200 rpm at a stop. When it starts warming up I can "manually" force it down into idle by releasing the clutch in gear while braking, which obviously chokes the engine to a near stall. It may stay there at first, but a few minutes later when the engine is more hot even doing this won't work and it'll just revs back up.

I guess it might be secondary air, I'll try the wd-40 trick tonight and see what happens. If someone else has seen this, please let me know what it was and how you fixed it.
 
Could be a vacuum leak but carbs out of sync will cause hanging idle problems also. What year 750? I always have to back off the idle speed screw anyways as my motor warms up. If you never touch your idle speed screw, your warm engine idle speed will always be higher than your cold engine idle speed. Warm engines have less friction and fuel vaporizes better and you have better combustion in a warm engine than in a cold engine. Cold engines have to pump thicker, colder oil and takes a lot more power to do so.
 
Must be something like that, I checked it out and there don't seem to be any vacuum leaks around the carb boots. Guess I'll try backing off the idle screw and see what happens.

Thanks mucho.
 
Back
Top