Partially locked up motor? Help!

[geez]

2 months ago my 16 yr old had a rock damage the oil cooler and the oil pumped out unnoticed by him. Long story short, I don’t know how long it went w/o oil. Added oil. Ran fine till last Friday. This is the story I got. Going up a hill, the motor started tapping and shut off. Almost impossible to kick. After 1 hr. it still kicked very hard but started up and was still tapping. He shut it off immed. Towed it home, pulled the plug and I checked it and it was very hard to kick, I am 250#. I tore it down including splitting the cases. 1st thing I found was the white camchain guide was melted and destroyed in 1000 pieces. The exhaust rocker roller was pitted badly and the cam ex. lobe was not looking too good. No oil? After removing cam assy, crank spun freely and quietly. I was worried about those factory crank problems, so I removed the crankanyways to at least flush the plastic pieces out.Crank looks absolutely perfect. Cam also spins freely and quietly. Oil suction screen totally 100% plugged leads me to believe no oil in top end. I can not solve why, where the motor was 85% locked. Ordered new cam and cam bearings. Probably will put orig crank back in. Anyone with any suggestions what else I can look for or any suggestions would be greatly appreciated.

[400exrider707]

Originally posted by geez
2 months ago my 16 yr old had a rock damage the oil cooler and the oil pumped out unnoticed by him. Long story short, I don’t know how long it went w/o oil. Added oil. Ran fine till last Friday. This is the story I got. Going up a hill, the motor started tapping and shut off. Almost impossible to kick. After 1 hr. it still kicked very hard but started up and was still tapping. He shut it off immed. Towed it home, pulled the plug and I checked it and it was very hard to kick, I am 250#. I tore it down including splitting the cases. 1st thing I found was the white camchain guide was melted and destroyed in 1000 pieces. The exhaust rocker roller was pitted badly and the cam ex. lobe was not looking too good. No oil? After removing cam assy, crank spun freely and quietly. I was worried about those factory crank problems, so I removed the crankanyways to at least flush the plastic pieces out.Crank looks absolutely perfect. Cam also spins freely and quietly. Oil suction screen totally 100% plugged leads me to believe no oil in top end. I can not solve why, where the motor was 85% locked. Ordered new cam and cam bearings. Probably will put orig crank back in. Anyone with any suggestions what else I can look for or any suggestions would be greatly appreciated.


A guy I know did this. He rushed putting his motor back together one time and just slapped in the cam chain tensioner. This put way too much pressure on the chain, and it melted the cam chain guide like you said. he shut it off, not knowing yet, let it cool down, then when he went to go out for his moto it wouldnt kick. The melted pieces of cam chain guide stuck to the chain and caused it to "lock up" He jumped on the kicker and snapped the cam chain.

[geez]

Thanks, 400exrider707
Got me thinking. wonder if it is possible the cam chain got so hot that the tensioner acted in a way to compensate for the increase in length due to possible overheating and when cooled down, the camchain is extremely tight. can anyone explain the inner operation of the tensioner. is it a ratcheting tightner or a continously springing action. don't know how to better explain!
m

[400exrider707]

Originally posted by geez
Thanks, 400exrider707
Got me thinking. wonder if it is possible the cam chain got so hot that the tensioner acted in a way to compensate for the increase in length due to possible overheating and when cooled down, the camchain is extremely tight. can anyone explain the inner operation of the tensioner. is it a ratcheting tightner or a continously springing action. don't know how to better explain!
m

It is a continuous tension. You back it off using a small flat blad screwdriver in the back. (under that phillips cap). Once you let go it springs against the cam chain guide. I dont think the cam chain can really stretch that much, then cool down and be tight. I see what your saying and in theory it sounds possible, but I dont think it gets hot enough to stretch that much. Low oil could definitely cause heat and cause that plastic to melt. What was the oil screen plugged with exactly? That would definitely cause the oil to not pass and result in overheating.

[Harbin_22]

Just to let you know on the oil screen thing, there is a bypass in case the screen gets plugged oil will still continue to circulate. Clean everything out really well. It probably wouldn't hurt to get a new oil pump since it might have went dry. they are cheap too.

[400exrider707]

Originally posted by Harbin_22
Just to let you know on the oil screen thing, there is a bypass in case the screen gets plugged oil will still continue to circulate. Clean everything out really well. It probably wouldn't hurt to get a new oil pump since it might have went dry. they are cheap too.

Yes good point, I forgot all about the bypass.

[geez]

The screen was plugged with the camchain guide plastic pieces, but if there is a bypass, he probably had oil to the top end. I am pulling my hair out trying to reason why this motor partially seized. I can find no reason yet. I hate to dig into a motor and not be 100% sure what went wrong. Thanks for the suggestions and help so far!

[400exrider707]

Originally posted by geez
The screen was plugged with the camchain guide plastic pieces, but if there is a bypass, he probably had oil to the top end. I am pulling my hair out trying to reason why this motor partially seized. I can find no reason yet. I hate to dig into a motor and not be 100% sure what went wrong. Thanks for the suggestions and help so far!

Well what exactly do you think seized? Are you just trying to figure out why the cam chain guide melted?

[geez]

still trying to figure what seized. i just degreased everything. found some alum dust but can not find any rub points. When i do put this thing back together, what, if anything is used to apply to the crankcase gasket? I have always used yamabond on case halves where no gasket was called for?

[400exrider707]

Originally posted by geez
still trying to figure what seized. i just degreased everything. found some alum dust but can not find any rub points. When i do put this thing back together, what, if anything is used to apply to the crankcase gasket? I have always used yamabond on case halves where no gasket was called for?

Just use the gasket for it... order the case gasket for it. Im not a fan of using bonds in those areas because it is far too easy to block off an oil passage or something.