Odd engine rythm when not on the gas

[ousidethebox]

had the same symptoms with my 3rd vmax, popping thru exhaust and sometimes carbs. uneven and missing during cruise but seemed to clear up when hammer down. problem got worse and worse. no amount of carb cleaning or synching fixed the problem. no one seemed to have the answer. one night i dreamed of performing a leakdown test. so i did. turns out the problem was valve clearences. the shim under bucket type valvetrain tightens up as it wears over time and usage. valves behin to stop sealing and symptoms get worse. valves then burn and pit. power goes away etc... i removed engine then the heads and resurfaced and hand lapped the valves. put it all back together. valve clearences were way off of course. ordered new shims and installed them as needed. totally fixed the problem. it is easy enough to check valve clearences with the engine in the bike. a leakdown test isn't much harder. might be worth looking into. good luck, cheers

 

[Jayhawk]

Ok, sort of hard to explain, but basically when i am rolling along any speed (eg 35mph for example), i am holding the throttle slightly open to maintain speed. Instead of giving an even Purrrrrrrrrrr sound, it almost sounds like it is missing, but you can give it boot and it does not miss at all. Sort of feels like it is getting worse, and is not so smooth on take off unless the revs are up.
A few things to note:

*I had the carb's sync'd 2 weeks ago, had problems with backfiring thereafter, went to yami (different place) they said the carbs were out of sync. I have checked the linkage for setting t e carbs during sync and it does not appear loose. It has a slight forward back movement on the sleeve but no wear when you try to swivel it so no obvious wear IMO

* I have opened up the stock exhaust (first there was small hole put in the baffle - made it a little more deep sounding, but not louder. Then i drilled 1/2 inch holes in the backs of them.

When the carb's were re-sync'd and tuned this was all done at yami with the open exhaust (which the mechanic was not impressed about saying "you've F**ked your exhaust" pointing out how one exhaust handles most of the load and is balanced by the other exhaust.

I am planning on getting the carbs rebuilt in a week or so as the bike sat for a long time prior to me buying it.
Is it the carbs that are probably causing this issue or could it be the exhaust?
Are the carbs potentially going out of sync again? And if so, why??

My bike does edzachary the same thing. Anything other than maintaining a light throttle and it runs great. Just cruising (at light throttle, not at higher speeds) and it surges a bit, sometimes dropping a cylinder in the process. Sean's explanation below is pretty interesting.