Engine Seized - Please Help

[Water Warrior 2]

If the plastic guide was holding back the engine from rotating you may want to put your energies there. Why did it get out of position ? Possibly it is in need of replacement. How is it held in place and will it come undone again if it is in poor condition.

[Easy Rider]

Originally Posted by PeterSeymour

but a reality check may be what I really need given the severity of these issues.

See my previous answer.
You likely are just making matters WORSE instead of better.

[alantf]

Originally Posted by Easy Rider

your only practical recourse probably is to sell it for parts.

THAT was your last suggestion. He'd probably not get much for a siezed engine, so what's he lost by trying to repair it? Also, Peter, even if you fail, it's a great learning experience. I say "go ahead". If you succeed, you can be proud of yourself. If you fail, it's nothing to be ashamed about. :2tup:

[Water Warrior 2]

Peter it will be a learning experience for all of us. Keep at it. If it is really broken beyond repair you have nothing to loose and if you can repair it we all win and you are on the road again. Pics are always a bonus.

[PeterSeymour]

Well after bringing it in to the machine shop where I work and doing some further deconstruction I discovered the problem. Once I saw what happened it really was quite obvious and hopefully the information could help someone else on here some day. I only have pictures of the piston now, but I will take more of the bike and post them tomorrow.

One of the four exhaust valves on the bike broke at the base of the valve stem. I am not sure what caused this to happen but it solves all of my questions. After breaking the valve head was floating loose on top of the piston within the cylinder which, combined with missing an exhaust valve, I think caused the high RPM issues with the motor. I am fascinated though that the bike was able to run with an 1/8" thick valve sitting on top of the piston and a missing valve - in fact it actually ran fairly well with reduction in performance only at high RPM. The continuous impact between the piston, valve head, and cylinder head caused sever damage both to the surface of the piston and to the head. The piston is cratered beyond belief in addition to being completely warped. I think this warping may be responsible for the oil loss as the piston did not form a complete seal in the cylinder. As far as I can tell, the only reason the bike stopped running and "seized" was because this flat chunk of valve somehow got turned on its end and with the piston now hot embedded lengthwise into the top of the piston. This impact caused a massive gouge in the piston, cracking it and almost bursting right through the piston, and prevented the piston from reaching top dead center. As a result the engine would turn almost one rotation and the metal clunk was the piston hitting this remnant of the valve. Unfortunately I have no way of knowing if all these impacts also affected the tie rod and the crank, but I imagine that such an impact could not be good for the tie rod or any portion of the engine.

I still really do not know why a valve would break off like that, other than it just being bad. The last valve adjustment was only 2500 miles before this incident so I don't think it was neglect of adjustment. Nor do I understand how this engine with only one cylinder was able to run so well with a valve not only missing but stuck inside the engine. I don't feel too bad though because once the valve broke I don't think I could have done anything to completely prevent the ensuing damage and even a few impacts would have left the engine in need of a complete rebuild. My only questions are is it worth dropping the engine and trying a top end rebuild when I do not really know the status of the crank? And if I decide to part the bike (which I most likely will) how much can I expect to get for it - it is in nearly flawless shape apart from this engine blow up (almost new tires and brakes, recent shock/fork tune up, clean body, etc)? Also should I try to sell it as a complete parts bike or should I pull everything off and sell each component individually?

Thanks for all the help, if you have any theories as to why this could have happened I am really curious. I will post more pictures later, but here are some of the piston.

[burkbuilds]

Wow Peter, sorry about all the engine damage, but I love your "jump in there and figure it out yourself" attitude. Way to go. You probably now know more than most of us about that engine. If I had quit every time somebody, (usually my mother) said, "you don't know what you are doing, you're gonna mess it up." then I never would have learned to do all the things I now know how to do. Oh, and yeah, a lot of times I did make it worse, but how else you gonna really learn something than to dig in and tackle it? Anyway, you should be proud of yourself for the way you tore into that motor and solved the mystery.

[blaine]

That's really to bad. As to why it happened is anybody's guess. :??: I would think you will get more by parting it out than selling it complete.

[Water Warrior 2]

Wow, did that piston take a beating. I'm surprised the valve top didn't just smash the entire piston top to pieces. As for the valve breaking off the valve stem, that can happen. It is fairly rare but I know it does happen now and again.
The engine might be repairable but I doubt it would be a cheap project. Maybe just pick up another used engine if you want to keep the bike and ride it.

[Easy Rider]

Originally Posted by PeterSeymour

I still really do not know why a valve would break off like that, other than it just being bad.

Nor do I understand how this engine with only one cylinder was able to run so well with a valve not only missing but stuck inside the engine.

There are too many unknowns to get a really good answer, the main one being: Did the oil get low before or after the valve broke? I think it's a good bet that the oil got low first and NO OIL caused the valve problem. But that's just a guess and you likely will never know for sure.

Trust me, the engine did NOT run "so well" AFTER the valve came completely loose; it won't run at all with the exhust valve wide open. That spell of running different likely happened when the valve stem first strated to crack OR when the engine started to overheat due to lack of oil. If you had stopped running it at that point to investigate WHY it started runnning so differently, the valve might not have broken.

Hind sight is often 20-20 but, in general, any time an engine exhibits a drastic change in how it is running, it should be shut off and not run again until evaluated by trained personel.

I expressed my opinion about what you should do next already and that hasn't changed as a result of your latest discoveries. The fact that you work at a machine shop might make a little difference but I don't think you can trust that engine again without a complete rebuild. The only things likely not affected are the transmission, clutch and cams. You certainly need a new cam chain guide and that makes me wonder if the chain didn't experience and extreme stress too.

A "new" engine would be MUCH easier......and probably less costly in the long run too.

[alanmcorcoran]

Good report. I'm not the best source of engine vs buy a new one. Seems like you learned a bit about the innards here, but I don't know that there is an economical source of replacement engines to work with. I've seen Geezers for under 1K to buy whole - might be easier.