620 With Whining Noise (Solved!)

[thorn14]

A couple months ago, a mile from home I started getting heavy vibration and loss of power. It also produced a horrible whine. I've only just got to taking both side covers off and checking for issues. It was leaking oil from the layshaft seal, and I suspect the valve guide seals on my vertical cylinder (both seals were black and I read one was supposed to be green). So the oil level was fairly low.

The loss of power I want to blame on the gas tank I had swapped to because my old one was leaking. I have since changed the filter. But I can't test for loss of power because I can't ride it under the same conditions so this may be a non-issue.

The alternator magnet rotor thing (don't remember the name) that spins with the flywheel was loose and the bolts holding it in were only finger tight. I noticed it wobbled enough to also touch the alternator coils in a few places. I attributed this to the vibrations I was feeling. I also replaced the bearing in the side case as it sounded bad just spinning it slowly.

Last night I fired it up after solving those issues and I still get a loud whine that can be heard inside the house even over the exhaust at idle. I've checked both clutch and alternator/flywheel sides for loose nuts and I get nothing. I did have a silvery sheen to the oil when I drained it which leads me to believe it is aluminum (fine dust).

That is all background, so basically, I'm assuming that a bearing somewhere in the cases is making a racket. Is there a way to pinpoint where the noise is coming from without splitting the cases, or any other places to check? Thanks.

[OzzyRob]

Thinking aloud again, and really hope I'm off mark.

I'm thinking it could be a main bearing, due to the loose item on the end of the crankshaft.

Can you feel any movement at the fylwheel that shouldn't be there ? ie side to side or up & down ?

[SpikeC]

 Silvery oil is very bad news. It sounds like tear down time to me.   

[thorn14]

Finally got around to solving this issue on the old 620 (aside from swapping in an 800 engine).

On original inspection I never removed the flywheel, only retightened it and proceeded to fire up the bike after checking case bearings.

This time, I took everything off, and now am down to the cases. (Which I can't split easily at all, any tips besides a rubber mallet?)

When taking the flywheel off, I discovered a bunch of fun exciting things.

Not only was the flywheel dug into pretty intensely, when I took the flywheel, and gear off, the bearing that fits inside the gear fell apart with roller pins spilling everywhere. I'm assuming (as now I can't just fire it up) that this was the noise I was hearing. So I'm also going to assume it helped chew up my flywheel, and attributed to the silvery oil.






This was the only red flag on tear down. Everything else including case bearings seem okie dokie otherwise.

[thorn14]

Follow up question.

Is this flywheel able to be used again? Could I machine it down a little to smooth it out? Maybe fit a washer in between the inner mating surface that got ground away and the gear?

Is it safe to sell even? Or do I have a new paperweight?