Was riding home on the Stella Friday and it suddenly started running a bit off. About a half mile down the road from there it seized up completely resulting in a pretty sketchy rear wheel lockup at around 50mph. I was able to clutch in quickly and keep the bike upright, but nothing I could do on the side of the road would get the motor to turn over.

I got it home and tore in a little bit

Fully cooled down everything was still completely locked up.

The head has a bunch of debris damage around the squish band

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The piston has similar damage and what appears to be a needle bearing embedded.

Not good.

It appears something in the bottom end gave up and proceeded to quickly grenade the rest of the motor.

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I’ll update more once I figure out how to tear the motor down further, right now it’s seized at TDC and I can’t split the case with the jug still on.

Thankfully, worst case scenario, I can get a fresh complete motor for about $600 if nothing in this one is worth salvaging.


(Update 9/24 PM)

Tore in a little further tonight. Got the motor out of the bike.

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Got the exhaust off and that allowed me to beat the jug off with a hammer.

The piston has DEEP scouring, not going to be good for much other than a neat desk toy.

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The cylinder fared a bit better, being made of a noticeably harder metal. Still cylinders are cheap enough to make reworking this one not worthwhile.

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Everything inside is coated with fine copper flakes.

The crank is totally seized at the big end. I tried everything I have on hand to free it up but noting. This is the failure point. Reading online, there was a tolerancing issue on a bunch of these that causes the bottom end to go. It appears that’s what happened here.

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And that’s where I’ll be for a while. Next step is to split the case, but I’m waiting on a flywheel puller to get any further.