Today I replaced my head gasket on my 91' lt250r quadracer. It was rebuilt before it bought it but I do not know when. On top of the piston it says 75mm. What does that mean? is it bored out? if so how much. Stock bore and stroke is 67x70 mm. stock piston is 66.915 - 66.930 mm.

Also I am going to rebuild it this winter, I am looking at two kinds of pistons. Niks Pro X it is a single ringed high domed racing piston. Or a wiseco piston. Which one would be better? any other suggestions for pistons please post.

thanks,
-chuck

 

I havent tried that niks prox piston but i was happy with the wiseco pro lite kit. i thought that pistons usually have their oversize written on the top....so 75 would be 0.75mm oversize? someone will have to confirm that. it means 0.75mm over the stock bore size.

 

It is not the bore, 69mm or .080 over is the limit for this quad.
I have never had any problems with wiseco as long as you left around .003 clearance.

 

ok maybe i said it wrong...i didnt mean the bore size...the piston size over stock. therefore you should have a 0.75mm oversized piston...not much before you need a resleeve