Hey, I have a seized motor in a 92 rm 80, i am going to rebuilt the top end and my question is if I used a 100cc jug, head, and piston? Are the bottom ends the same and rods? Because i got thinking, why make it an 80cc if I can go with a 100cc. So if i was wondering if they were the same botom ends because I know that kx and some other brands are. Just want to make sure. Thanks ;)
No there were no RM 100's made that are compatible with your RM 80. The only way is to have the engine built into an RM 100 from your existing 80 cc motor.
You could bore it .080 over and its not going to be 100CC's ... You'd need some kind of stroker crank, if they make one. Or a big bore kit with an oversized sleave that lets you bore more than .080 past stock clyinder size.