One of my riding buddies has a 91 DR250. He got it a few years ago with a 20 or so miles on it from the original owner who won it at a race. Anyway, he changed the oil a few times (in two years). He cleaned the oil fiter once. A few weeks ago it started to rattle really loud. It ended up being a craked in half kicker gear. He gutted the remaining gears and just pop started it. Last week it started to over heat. It got too hot and lightly seized the piston. He took it out today for a few minutes and it was running great but then it started to get really hot again. He shut it down and we tried to figure out why it was getting hot like that. We checked a few things and realized oil wasnt moving from the res. He said he blewout all the lines and they were clean. So i checked the oil filter. It was so clogged with clutch debris that oil couldnt flow through it. All it took was new oil and a new filter and the over heating is gone. the morale of the story is keep up on the maintinence because motor rebuilds arent cheap.