jetting, is going flat mean its lean?

[YZROOSTINYA]

when I rev up killas quad about 3/4 up in the rpms it starts to go flatter and sorta stumble.

it doesnt bog

i am thinking its lean?

Could loose valves(to much gap) cause this also?

[MOFO]

next time you rev that mofo up to 3/4 throttle, do it for about 20 seconds then hit your kill switch while its rev'd up. Pull your plug out and look.... sounds like it maybe rich to me.... i had a mainjet fall out :eek: during a harescramble before (my bad)...did the same thing as yours...but worse. Play around with the main jet...