I havent had a dirt bike since I was a kid, and would love to dink around on one again. The guy selling it didn't even know what it was. It was listed as "Suzuki dirt bike, doesnt run". He was asking $150, but I knocked it down to $75. Its not in the greatest shape, but I've seen worse.
I noticed right off the bat that the compression was not where it should be when I turned it over. Being an old bike, I figured it just had a stuck ring from old castor oil or something. I hoped it would just loosen up on its own.
Well, it didnt.. I pulled off the exhaust and found this:
So it was time for a top end rebuild. Bottom end and wrist bearings felt perfect, so I left them alone. Found a NOS .50mm genuine Suzuki oversize piston on ebay, along with set of new rings. I did some calling around to some machine shops. Lindsay Machine Racing is the best known machine shop around for this type of work, but they wanted $90 a hole to bore! I called around to some other shops. Most wont touch 2 stroke cylinders, due to the ports. I found some guy that would charge $30, but he didnt sound very confident. Then I called a machine shop that a buddy used for his 22re head work. "Crankshaft Grinders". Very nice, knowledgeable older guy, with some younger kids working for him. $40 to bore it over. The exhaust port had some damage from the rings mashing against em, but most of that got worked out during the bore. He did an awesome job. I took a new ring, and checked the endgap from one end of the cylinder to the other, and it was spot on! I'll be re-using this guy in the future with the CB200 I have. He chamfered the exhaust port, and I chamfered the rest:
Cleaned it all up, a touch of assembly lube, and its time for re-assembly:
The bike immediately had monstrous compression compared to the way it was! It started right up after about 4 kicks:
Thats about it for now. It needs to be broken in. The bike still needs a lot of other work. Tank is rusted out, needs a chain. Tach and speedo are missing, but I dont really care about those. Oil injector is not hooked up, so it runs premix. But it has a pressurized crank oiler, so I should get that working again. Should prolly get a title too