hey, i've had major engine problems as of late as well so i'll give your problem a shot. hope it helps. obvious things first, try replacing the glow plug and charging the ez start battery. i'm sure you've done both of those, but just throwing it out there.
if that stuff doesn't or didn't work, i'd take the engine out of the truck and tear into it to see if there's any damage to it, maybe from over heating. if things look good with piston head and sleeve and the bottom of the cooling head, lube it all up with some after run oil before putting it back together then try it again.
have you recently leaned out the engine at all? my problems all started when i leaned mine a slight bit and the added power was too much for the clutch. i should've tightened the slipper clutch nut at the same time but didn't. after that, when i ran it it stopped shifting into second and the rpms were through the roof. it took two quick speed passes at the high rpm level and that was it. take a look at the thread also under the revo section about not having and idle. there are some pics of what happened and a pretty detailed discussion of what i went through as i discovered what the root problem was...
