Ok, I bought an xt350 for really cheap. I fixed it up a little cosmetics and mechanicaly. I put a new piston in it, had some score marks on the intake side of the piston. Ran it and it partial siezed in a couple of mins riding. i pushed it home and took it apart. What i found was a seizure marks just in the intake side of the piston. So i bored it out thinking maybe the bore was crooked and put another new piston in it. Same thing. I took it apart to look again, same intake side smearing meatal look. I rejeted with a 130 out of an xt600 and shimed both needles thinking it was just a little lean. Same thing. The air boots are good, all the gaskets are good. It actually sounds really good when it running, doesnt pop, idles well, just seems to run great. I cant find anything wrong. It does get hot before it seizes, but frees up right away. So, what the * is going on? I was wondering if the piston is oiled just by sling? Or is there more to it. Does the oil pump oil the piston in anyway? My book is pretty hard to get the info you need out of it. Please, if you have a good idea please Help. Anyone ever have a problem like this? Thanks in advance for replies!