(16-05-21, 09:24 PM)unfazed link Wrote: since you appear to have ruled most of the obvious things there is one other possibility, one or more of the much forgotten Air Cut also called the Accelerator Pump diaphragms has a hole.
This can give the symptoms you describe poor initial acceleration and backfiring on deceleration on a fully closed throttle.The unfortunate side of checking them is that the one on the left is easy to get at to check but the other 3 need the carbs to be separated to check them.
The reason behind it is to provide a dash of fuel for quick throttle opening from idle and at closed throttle on deceleration to stop the lean popping in the exhaust .
It has caught out many a mechanic. I first came across the issue on a Ford Cortina way back in 1979 and a few Hondas and Suzukis since with similar issues. Most fellows replace the carbs without checking it which is why you don't hear much about it.
I've always ripped out the air injection bollox on any bike I've owned with it fitted, I never mentioned this potential issue, I just assumed the air injection crap had already been removed & smashed with a 4lb hammer like it deserves ... lol :rollin