"Sounds to me that the carb is running low on fuel and when it "catches up" (fills again) then it will run until it gets low again."Sounds to me that the carb is running low on fuel and when it "catches up" (fills again) then it will run until it gets low again.
Assure the float bowl vents are not obstructed and the fuel tank is venting properly. If that checks out, then check for an obstructed or kinked fuel line, an obstructed petcock or clogged fuel filter.
It may be an over heating issue and it may ultimately end up being an ignition issue.
I had a KX125 Kawasaki that was completely rebuilt (engine, suspension and all bearings) - it ran great most of the time, but it was temperamental. Some days it was hard to start, other days started easily. Some times it fouled the spark plug repeatedly and then it would run for weeks with no fouling (it was pre-mix so I know the oil to fuel ratio was not changing, I always use the same gasoline, oil and ride at the same appx. above sea level) - in a final attempt to solve the issues, I replace the one part that was still original - the stator. Immediately the bike started better, had more power and no longer fouled spark plugs. The stator solved the temperamental issue.
Let us know what you figure out, but I think you can quit fooling with the carb.
That was exactly my thought and why I spent so much time on fuel supply and carb. I have given serious thought to replacing the stator as the bogging is so random. One run up a hill it goes 1/4 way boggs, next is 3/4 way, then right off the start. But when I do an open spark test the spark seems very strong. When I first checked the timing it was 100% (max adjustment) advanced. So I think someone who didn't have much mechanical experience may have worked on it previously so who knows what I'll find once I get the flywheel off. Never had this much problem on a machine before. I've been a mechanic in one form or another (automotive, construction, forklift, marine) my whole life. Can't believe such a simple little machine is giving me such a headache.