bike refuses to run smooth

[Black wing]

so my bike has been running me in a loop for a month now, a while back i put a new exhaust on it and tuned the carbs it ran beautiful for like 20km pulled like a freight train and was super smooth was better than ide ever had it. then after 20 km or so it began to run low on power again, having to run almost full trottle to get my bike and trailer up to 120kph and the milage has dropped from 32 mpg to 23 mpg.

 

so far the issues ive seen is when i did the valves all 4 on cyl 2 were out of spec, after the 20km and things began going down hill i found that the rear 2 cylinders were not really firing i could pull the plugs and the sync caps and the idle and rev wouldn't change, replaced the rear plugs and it got a little better for a short while. then the boot over cyl 2 began getting really wet.

 

now ive gone into the carbs to see if anything was off and they were pretty well spotless, the fuel levels were low so i adjusted them and that seems to make it a hair more peppy but not what i had right after the tune. and now i cant get cyl 2 to stop popping on idle unless i turn the air screw all the way in. no vacuum leaks anywhere and the sync is spot on

 

i just have no idea whats making it run so crappy, all the plugs are new, wires are new, carbs are spotless, valve are adjusted, exhaust is well sealed, the tci is a new ignitech. i just don't know where to go next. what could possibly be making run so crappy?

[frankd]

Do you have good spark to the rear cylinders?

[easternrider]

I am going to guess that you either have a diaphragm leak/bad slide, or you have an ignition coil breaking down when hot.

My bike does similar thing. All my diaphragms are good, and after a 20 min run, it starts to run rough, and RPM's drop by about 400rpm. I am soon going to start replacing coils till I find the one that is bad. (at least I think that is what it is).

[Black wing]

its not a heat thing it just runs rough from cold to hot, they test good and when i took the plug out when hot and still had fire on doth side when i grounded the plug to the frame, though i do notice from time to time the bike will hic up and the tach will drop to 0 for a second then spring back up

[Flyinfool]

its not a heat thing it just runs rough from cold to hot, they test good and when i took the plug out when hot and still had fire on doth side when i grounded the plug to the frame, though i do notice from time to time the bike will hic up and the tach will drop to 0 for a second then spring back up

 

That part sounds eerily similar to the issue that I was having on my home from Dons MD. Except that when it was running it ran great. The tach is driven off of #2 cylinder coil. So if the tach is dropping to zero durring the hick up it means that #2 coil is not being told to fire. In my case it was all of the coils not being told to fire hence the noticeable hiccup. A single cylinder dropping out momentarily would never be noticed while riding. Mine started out as a hick up and progressed to a full blown shut down for several seconds or even minutes at a time.

 

I found 3 separate possible problems, one was a bad connector in the frame ground wire. one was a broken kill switch, and the other was a bad factory crimp in the wire the feeds power to all of the ignition circuits.

But like I said, mine never ran bad, just the occasional hick up.