Well, the point is the chinagirls aren't exactly balanced or blueprinted lol...I've had 5 of em, and they all danced a little different.
When you spin an engine 6000RPM, the crankshaft is spinning over 100x a second
! Think about that!
Any imperfections in balance will be magnified of course, so if you get an engine that's off, really, what can ya do but lower the revs?
I have kind of a built-in rev-limiter myself..I don't really like spinning my engines over that 6K mark.
None of my 2-strokes liked it either. With my 34T, they purred happily.
My 4-stroke does 30MPH at 6K RPM, and it makes maximum HP at 34