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

1982 CB900F, Now posted in correct forum

Rcb1000

CB750 Member
Messages
12
Reaction score
0
Points
1
Location
Alabama
If AMC49 is out there, per your suggestion, I broke broke carbs apart and went through them again using MacGregor instructions. The carbs are clean and all orifices open. I bypassed the air cuts as recommended. Put all back together. New dr8ea plugs (could not get dr8es). Pilot screw 3 turns out as recommended to account for air cuts bypass. Bike ran great. After 3rd ride, bike bucked at low rpm, ran great at high rpm. Pulled plugs, coated with black carbon like soot. Figured running rich. Cleaned plugs, reinstalled, set pilot screws 1 1/2 out (leaner). Bike ran better at low rpm longer before acting up. Pulled plugs, still slightly sooty black. Will I hurt anything turning pilot screws in further? Should I go with hotter plug? Would you suspect bad coils or igniters (they look original)? Any advice would be appreciate.
 
I always ran 8 plugs and a is virtually the same as s. I ran non-r plugs to use the resistance at the gap instead by opening gap a bit.

When you block the aircuts you block off like one half the idle air, may need to even drop back slightly more on mixture screw.

If due to engine condition the throttle is slightly open too far then the hole behind butterfly exposes too much and the idle then goes rich. That hole is supposed to just cut off at normal idle and it exposes to go right as soon as the slide even thinks about lifting. Older engines force you to give them more idle air and normal and sometimes you have to play tricks to get engine not to run too rich at dead idle.
 
Thank you for the quick response. When you say "drop back slightly more on the mixture screw" do you mean turn it in more or turn it out more from the 3 turns out I originally had? Thanks again.
 
Back
Top