Vintage Dirt Bike Q & A

OKay- I have worked on alot of Honda XL motors doing top end jobs and such. This is my first 2 stroke rebuild and albeit much simpler than a 4 stroke, when a piston becomes seized in a 2 stroke they are really seized!

My MR250 resto project is a sad story, I bought the bike for a mere 100.00 bucks, mainly because it was all there with the exception of needing a tank, sprockets, seat, cables. The sprockets are the worst I have ever seen and looked like fish hooks for teeth. the OEM rear tire is bald in the middle as though it had been run on the street and or had done alot of burnouts, I suspect the latter. The engine is locked up tight as a drum. I have been soaking the piston in a mixture of motor oil and liquid wrench and bangin on ir with a wooden 2X2 and 5 lb sledge, it won't even begin to budge. The bore looks smooth down to where the piston is stuck. Once free, I plan on an overbore and of course new piston and rings, bottom end bearing and seals. I may send the crank off for a professional rebuild so that the rod big end bearing can get replaced. I also need to replace the countershaft while I have the cases split., as the countershaft sprocket I think has been spinning on the shaft and beat it up badly, the countersprocket was missing several teeth!

This motor sadly was completely ruined, mud, silt sand has gotten into the internals and the crank and bearings were completely rusted / frozen soild. Cut the piston in half in order to remove the cylinder. Needless to say it is pure junk. Crank looks like a boat anchor after being on the bottom for 30 years, shift shaft bent, 2nd gear missing teeth, not much salvageable. Probably just toss it. gimme a holler if you want the left case (right is broken) head is okay, jug is maybe ok - rough on top. some gears ok.

That is too bad. Don't give up. Here is the lower end of an engine, could probably use your left case. Gotta hurry though, bidding about to end.

http://cgi.ebay.com/ebaymotors/elsinore ... enameZWDVW

Cylinders are relatively easy to find for these bikes. I'm guessing you may be able to bore yours.

Did you get the shop manual??