Motorcycle Repair: 1976 honda cb750 fast idle, 1976 honda cb750, vacuum ports

Question
hi, i hva a 76'cb750 and im at wits end with the carbs. i have set to all factory specs as a strting point and when i fire it up it idles at 3200 and not any lower. it does this even with the idle screw backed all of the way off. slides are adjusted down to a paper clip width all synced up. ive read that this could be a possible ari leak?? is this true, if so where would it be coming from , the boots??? any help would be awesome thanks alot -mike

Answer
Mike,

any air leak on the boot side may
affect the idle. The boots can
sometimes be checked by spraying
some wd40 or carb cleaner around
them and see if the engine speed
changes.
The rubbers can be replaced or sealed with
some high-temp silicon seal rubbed
into any cracks.
Check for any open vacuum ports also.

Have you first checked the timing
and the valve clearance on this bike?
Should be done before carb adjustments.

Have you checked the mechanical auto-advance
unit under the contact points?
If the advance sticks in full ignition advance
it might cause a speed up.

The sync screws can be a problem to
set and may keep it from idling down.
I remember messing with those to
get the idle and the sync right.
Back them off if necessary to
see if they are hanging up
the slides.
Are the float levels correct?
Air box and filter clear?
Do you have a vacuum fuel petcock?