we took a 2000- 500 motor , put an 11.5 to1 wiseco piston, 20mm over, put an HO cam aqnd 40mm carb, did a little mild porting on it and put it in my 425, runs really good, havent found a 500 that will touch it from 0 to about 55, then the old chain drive runs out of gearing, thats about all it will run but its quick, have put alot of miles on it and its been very reliable

 

my chain drive '95 xplorer dont run out of gearing at 55,....it cruises at 55 with barley 1/4 throttle...

 

your 2 stroke turns alot more rpms than a 4 stroke