Inconsistant Idle! What to check?

[WingMan71]

All,

I have a strange idle problem. The idle speed on my bike seems to change every other time I stop at a light while driving!

It's not a hunting idle, i.e. the idle speed does not surge up and down while idling. The bike just idles at different idle speeds from one time to the next. One time I'm idling at 870 RPM, the next time I'm idling at 950 RPM, the next time at 1040 RPM, etc. And yes, this is all with the engine warmed up and the choke off.

I have checked the throttle cables to make sure that they are not binding anywhere, and they seem to be OK. The carbs were synchronized about 500 miles ago. The engine runs smooth and strong at all speeds. The idle is even smooth, just never the same speed! No surging, no hesitation, no nothing, just this strange idle speed inconsistancy.

Any ideas on what I should check would be appreciated. Thanks.

[GTi Giant]

Mine does the same just to a smaller extent, I notice that it fluctuates the most when the fan kicks on (about 700rpm jump). Could that be the case withyours as well? I plan on syncing the carbs up this winter when I go through more of the bike.

[William_86]

that sounds like a vaccum problem, my friend's VF750 had the same problem and it turned to be worn vacuum diaphragms