yz250 opinions

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3/18/2018 5:19 PM

Hoping to hear what some of you have to think about this. My brother broke a piston on his yz250 recently, hours are unknown as he got the bike secondhand. the piston had a black spot under the piston, so I was suspecting crank seals as well. When I got the cases split I noticed that some hack has been working on the bike before. It looks like the po probably had the shift stopper come apart and rattle around in the transmission, and did a poor job with working on it. It was sealed with what looked like household clear silicone, on top of the original yamabond. Additionally there are pry marks and gouges all around the case, which appear to be from screwdrivers. I have two questions for you all.
First do you think these cases will seal with the spec yamabond, and a couple of gears in the transmission have a wierd copper coloration (I haven't tried to scrape it off yet) and was wondering if you had any Ideas as to what that may be?
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3/19/2018 4:33 AM

You can try matching the cases on a flat surface. If the gouges are too deep or damage mating surfaces, you won’t be able to use them without welding. Don’t remove too much material when matching them.

Once it’s all together, you’ll have to do a leakdown test to make sure they are sealing correctly.

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