Tickover trouble

[oldgreybeard]

My bike seems to have trouble ticking over smoothly. It will idle happily then revs suddenly climb to 5-6000.

I have cleaned the carbs, made sure that main and pilot jet in the jet block are clean as a whistle.

Air screws have been tried between 2 and 3 turns out but I still get the same problem.

Throttle Synchronisation at 1000-2000 revs seems pretty even across the 4 carbs.

I even bench set the fuel level in the float chambers with 4 pieces of clear tube. I had previously done this with the 14mm credit card method and found that there was quite a bit of variation in practice.

the head to carb rubbers are showing signs of age, but I cant see any splits right through.

Any thoughts. What are the symptoms of air leaks in the mounting rubbers?

[matzxr]

Spray carb cleaner around each inlet rubber see if revs rise.
Split diaphragms ?
Weak petrol pump ?

[YAMAEXUP]

As has been suggested, ti sounds more like an air leak. My ones were on their way out so I replaced them with the Foxeye inlet rubbers, as they come without the airdam web that restricts the earlier Exup-R models like my one.