Top end rebuild

[85 250sx]

hello im looking to rebuild the top end on the cr500 motor that i have for my 250r frame. ive never done a top end rebuild so a buddy of mine is goin to walk me along on this. well i started to look online "mostly ebay" and found lots of different kits and prices.
so what im kinda wondering is if there is any products or companys that are better or worse that i should go with or stay away from. also whats the differnce in wiseco pistions with the pro-x and pro-light and stuff like that Thanks!

[AtcFactoryRacer]

The difference is "Cast" and "Forged" pistons. I know wiseco and pro-x pistons are forged, which means they are lighter (less rotating mass = higher RPMS) and can handle higher rpms, high octane fuels, alcohol, NOS, etc.....but can shatter if you have preignition or overheat. Stock pistons are Cast, they weigh more (more rotating mass) but will melt instead of shatter if they overheat or preignition. If you blow the topend, Cast pistons will cause less damage to your crank(in most cases) can lack the quick acceleration that a forged piston can give you, But can be more reliable. There is a balancing point on the good and bad of both styles of pistons. It sounds like you are wanting a powerhouse by putting a 500 engine in an atc250r frame, I would put a wiseco piston in it, properly break in the engine, get the jetting perfect (burning a cinnamon brown colored sparkplug), Run the hell out of it.... but tear it down, hone the cylinder and re-ring the piston every 45-50 hrs and your piston should last forever.....

[85 250sx]

ok sweet! thanks for the help! i had it jetted and running great but the plug i rigged up to block one of the top end water inlets flew off while i was riding and didnt notice untill it was to late.