This is a second post looking for specific answers to fix my son's near-new yz85 (15hrs). It shifts fine at low rpm's, but wont shift from 3rd to 4th (or 2nd to 3rd) under full throttle. I'm inspecting the shifter mech. and it looks okay but only goes into the higher gears if i roll the trans axle, same thing coming down, which seems normal but i know nothing about the transmission. Ive changed four -stroke cranks but never had to mess with the tranny.