A stock one, whatever the crusher will give you, or maybe $20 on ebay.
Depends on how much you mean by excessive play. The secondary clutch sometimes should move a bit on the jack shaft because it needs to center itself.
it depends how fast you are going but they can go up to over 80 mph
Rocky Mountain King. it is a snowmobile designed not only for the trails, but off trails in deeper snow and big hills as well as mountains.
Once there is noticeable wear on them ( cracks, soft spots, etc.. )
answered on dootalk. 75W90 synthetic gear lube
Dumb question. Learn to gear, do clutch work, make the motor have more compression, and add aftermarket parts. A 500 could do 125mph, but stock it wont. The fastest stock sled is a 1998 Thundercat 1000 and it does 128mph when tuned correctly.
CLEAN YOUR CARBS! If that doesn't solve it, put a little bit smaller jets. If that doesn't work, clean your exhaust, you may have a nest in there, same with your air box.