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Bike broke down again

So what is the hard failure in the engine? I see a bunch of possibility of things that could contribute to the engine giving up the ghost. But nothing to really say here is the problem. I guess there was no hard part failure
 
ToSlow said:
So what is the hard failure in the engine? I see a bunch of possibility of things that could contribute to the engine giving up the ghost. But nothing to really say here is the problem
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That is a hard question to answer. Lots of maybes. Tearing it apart pre-diagnosis may prevent ever knowing exactly what happened. Its also possible that we haven't seen the major failure yet and what we have seen is collateral. Stiff bottom end is strange.
 
Note the black coating on the skirt of the front piston. This is a slippery coating that's meant to reduce friction. On that piston, it's in decent shape for a high-mileage engine. Now note the rear piston, which has bad scoring on one side, and on the other side, that coating has been almost all worn through. The cylinder heads don't look terrible. Pistons had a fair bit of carbon on top of them. It's pretty normal on an air-cooled V-twin for the rear cylinder to be running hotter than the front one. The scuffing on the piston skirt suggests that it was the piston that went tight, not a ring.

I still think piston-to-cylinder clearance was too tight, possibly in combination with some other cause of overheating.
 
Would extra engine air pressure cause the engine to become hotter?

I think the bike has been sumping. With the breather in a bad state, and blowing extra oil into the air filter, also maybe bypassing the rings/ and or oil pump. Bike did burn some oil. I could see and smell it on cooler days, not so much on warmer days.
 
Maybe it was so worn out that it didn’t have enough compression to keep running
 
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GreyGhost said:
Really unlikely that that would die at the side of the road and not restart.
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From the scuffing on the pistons and the carbon buildup in the combustion chamber this has been coming for a while. Time for a full top end overhaul and careful reassembly. No shortcuts.
 
GreyGhost said:
Why is there so much carbon on the gasket (rear cylinder head, exhaust port side)? Is that loose carbon from disassembly or hard? Was rear cylinder leaking out at head gasket?
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I'm not sure.
I know the rear rocker box was leaking at the back. At some point the exhaust wasn't butted correctly and may have stained it as well. But that was fixed before this breakdown.
The carbon on the underside is how it was when taken apart.
Also this cylinder the breather gasket was totally destroyed. I think it was puking oil out someplace.
 
OK decided to pull off the rest of the primary and stator cover to see the main shaft bearing and drive race for the clutch hub. Seems ok to me, everything rotates like it should. At least I know a bearing didn't blow. So it's looking more and more like a seize then anything else.

I'm really temped to just put it all back together and just to see it if turns over?
Bad idea?

inner primary removed.jpg
 
sburns said:
OK decided to pull off the rest of the primary and stator cover to see the main shaft bearing and drive race for the clutch hub. Seems ok to me, everything rotates like it should. At least I know a bearing didn't blow. So it's looking more and more like a seize then anything else.

I'm really temped to just put it all back together and just to see it if turns over?
Bad idea?

View attachment 62168
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I wouldn't do that. Button up the bottom end if you're comfortable with whst you checked.

I'd get a service manual and check the top end measurements before assembling. You likely need machine work, rings, maybe pistons too - no sense in re & re an extra time.

If evaluating the top end is outside your comfort zone, remove pistons then find someone competent to evaluate your cyl and pistons.

Get or fix components, then reassemble.
 
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