[Flip]

Originally Posted by FrankenDesmo

Do you mean the diaphragms? They're in tip-top shape, so no worries there.
'popping' might not be the best description. I'll be cruising at part-throttle, and around 4k seems to be the place with the biggest problem (possibly 3-4k), and it'll start to hesitate a wee bit if I 'adjust' the throttle - then if I chop a gear and open it up, there'll be a noticable hesitation right before it picks up and pulls as normal. Taking off from idle is fine, it's just that troublesome part of the rev range at part throttle.

I did indeed mean ‘diaphragms’ - damn that auto fill!!!

Ok next thought then- are the two little ‘air boxes’ still fitted to the frame?

Some people remove them to clean up the look of the frame (the fuel injected bikes don’t have them by default) but if the tubes from the carbs are not tucked into a still air space when riding on a steady throttle it can have the effect of blowing over a bottle neck and make the carb slides rise and fall as the pressure changes resulting in a kind of pulsing/hesitating sensation.