Vintage Dirt Bike Q & A

Went back 7 pages and couldn't find the usual question. So, I'm gonna ask it (again, I know).I jerked the motor outta the "new" bike and pulled the head off. Sure enough a big ol' hole in the piston. Saw the seal around the shifter hanging out and leaking too. Numbers on the piston top are 395 and 050. I'm guessing it's overbored 5 thou? Now for the question. Gonna need a piston, rings and seal/gasket kit. Who's selling them? Also, needing a throttle cable and tires/tubes. Used to be dennis kirk. Looked thru my old 06 catalog and had a hell of a time locating anything. Did see a wisco piston kit for around $110.00 (2 years ago). Any help?

Do you still have the manual I sent you?? I buy my seals from Honda, they aren't a bad price, but you can get the size of the seal from an online microfiche and maybe save a few bucks buying them from local seal supplier. Piston is about right in price. I have a guy at local Honda dealer I worked with 30 years ago, so he gives me little discount on prices and I think I paid $104 for my last piston. Go ahead and spend the $14 for new wrist pin bearing, too. I got my throttle cable from Dennis Kirk. My Honda dealer got me a Cometric top end gasket kit for $19 or so. Gaskets for both 73-74 and 75-76, so it can be used for either. But I would order a complete gasket kit from elsinorestuff on the 'bay. Great service and great price.
Now for the interesting part: 050 would typically mean 50 thousands over, which would likely mean you don't have a Wiseco in it. If you use wiseco, you'll have to go to .060 over (assuming your bike is .050 over now). If you do, you'll have to bore it over, which will set you back another $40 - $60 around here. Measure your bore and piston. 70mm stock. 71 mm .040 over and 72mm is .80 over. So if your measures 71.25, you're at .050 over (hope my math is right here). If you are at .050 over and your bore is nice, you'll likely have to find an ART piston to fit. Main difference is ART is cast and Wiseco is forged. Either should be fine.

Yeah, I still have your manual and the haynes (never get rid of books). In fact, I was going through all the paper work I had assembled during the last trip and found your old phone#. Has it changed? Would like to talk instead of type. Mind moves faster than my two fingers. Shoot me a PM w/ a number if you want to talk. Thanks for all the info. more to think about.

Yep. It's the same. Try to call during the afternoon, if possible. Phone is usually in the car overnight charging.

I have listed a MR250 gasket set if you are interested on Ebay. Jerry from elsinorestuff.