Sqealing sound

[wobbli]

Hi all,
My Mk 2 has started squealing loudly, a bit like a slipping belt on a car. Any ideas please?
It did about 20 miles yesterday before starting to squeal. It doesnt seem to matter if the clutch is in or not, but you can see the drive sprocket twitching even in neutral. I therefore drained the oil, no bits in it but it was low, and pulled the clutch side of the engine apart expecting to find a clutch problem. But nothing all seems in order. No sign of wear/burning, scuffing etc. (Dont currently understand why the drive sproket tries to turn even when the gearbox is in neutral, but perhaps someone will explain?)
It sounds like a dry bearing or perhaps a bearing truning in a casting. The oil was low, but Ok a few weeks ago. The engine dosent have any leaks, so I guess the engine is drawing some in through the crankcase seals?

Bit loathed to do a full engine strip but unless someone can come up some suggestions I can see this looming on the horizon.

Wobbli.

[knackeredMk1]

You will find that most bikes try to turn the drive sprocket at a very low pressure even when the engine is in neutral.

It is more than likely that the balancer shaft is making the noise. Most probably the the shaft it self is worn and/or the needle bearing. For more info - viewtopic.php?f=20&t=5536

Other opinions

[wobbli]

Thanks for the info. Might not get chance to have another look till the weekend but I will post what I find.

Do you know if the engine will burn gearbox oil by pulling it past the crankshaft seals or do I have another problem to look for?

Wobbli.

[fallenmikethebike]

Thanks for the info. Might not get chance to have another look till the weekend but I will post what I find.

Do you know if the engine will burn gearbox oil by pulling it past the crankshaft seals or do I have another problem to look for?

Wobbli.

Yes, that's the most likely cause, in view of a lack of any visible leak, replenish, with new oil, and monitor it's loss, use the level screw on the Right hand side to set and maintain the correct level.
Unfortunately, the damage may have already occurred.
Mike

[wobbli]

Hi all, stripped and rebuilt the engine this weekend. Didnt find reason for loss of gearbox oil, but rebuilt it with new main bearings and crank seals so I hope that will settle it. Found the source of the squeal. (Balance shaft and bearings were OK). It was one of the selector forks running dry in the gearbox. The groove on the gear has just started to pick up and the selector fork had started to go blue. Cleaned both with some fine wet and dry and reassembled with new gaskets and fresh oil and it appears to be OK. Total bill is about £120, and its taken about 10-12 hours.

Next time I think I will check the gearbox oil level.
wobbli.

[fallenmikethebike]

Well done, hopefully, should be good for a while to come.
Mike