Topic: '80 CB650c fine tuning question

[ABikeNamedTrouble]

Hey folks,

Well, after a couple months of work, I've finally got my 1980 CB650c running well and have put about a thousand miles behind me without any difficulties that weren't my own fault .

One thing has been bugging me:  when I let off the throttle to engine break, the engine jerks and runs roughly instead of a smooth slow down.  I'm also consistently getting around 40-45 mpg instead of the usual(?) 55 mpg.

Any ideas on what could cause this?  I have the mechanical slide (Keihin PD) carbs, and they're well synced.  I haven't noticed any other problems.

Thanks in advance for the help,
- Adam.

[cb650]

Air cut off on the carbs would be my first guess.

[ABikeNamedTrouble]

I would have thought the same, but the diaphragms are brand new and installed to spec.  I'm definitely new to motorcycle repairs though, so I could have missed something (not sure how though, they're simple devices).

[Zodo]

The air cutoffs have a little tiny air hole to the side when you take the cover off. Make sure that they have their o ring in tact and aren't blocked.