Found that there are these collars inside of the trans that the shift forks move and the collars have sprag teeth which engage in the gear sets to engage into H,L, or R. The sprags are square cut and if they wear they essentially become a ramp that given the right amount of load will instead of holding into the selected gear like a square cut will push the collar away from the gear set causing the bike to pop out of gear. Adjusting the shift rod one way will fix the popping out of reverse and adjusting the other way will stop popping out of high but since the sprags are worn down, it won't be able to work int both. The low range sprag is the same except adjustment may help a little more until heavy load is put on it, then it pops out. The root cause of this would be I imagine it would be the grinding sound that the bikes make when the rpm is too high and it is being put in gear combined with shift fork wear. I replaced the guts in my trans and it works perfect.
Bolt, for your bike go to the bike bandit web site, the part is #28 in the transmission internal illustration "dog, engagement, low" I would also suggest replace #19 "shift fork, low, sub-asm" if the ends of it look bent and/or worn or the detent groove looks worn on the shaft. The tips of the fork should have nubs and the detent groove on the shaft should be nice sharp cut v shape.
2001 TrailBlazer 250
1994 300 4x4
2004 Raptor 660R 727 Stage IV
2010 Eagle 110 mini utility
2003 Cannondale Speed 440
1951 Chevy Styleline
1972 Firebird Formula
2009 Wrangler Unlimited 3" lift
Last edited by speedhammer; 01-06-2011 at 04:35 PM.