I recently roached the piston in my 82 ATC 250R the problem was I don't know how I did it. I have taken it to Sand Lake Oregon about 5 times including my last trip, it ran fine for the first 4 times but on the third trip I was racing a stock and modified banshee and I noticed my engine smelling funny, then on the last trip I was not running it hard at all I went down to the pavement to go to the bathroom and was in 4th gear. I wanted to slow down so I let off the gas and then it died. After that it had no compression and after the 4th kick with no compression it siezed the piston. Could sand have been sucked into the air filter, it has several 1 inch diameter holes in the air box with the stock air filter. But the only thing I don't get is that it was running fine before.