Mystery graunching noise

[SeanW]

Hope some of you gents have some ideas on this - I'm stumped...

Have been rebuilding my R80 (see restyle project thread) - and in last couple of days I refitted the swingarm, bevel box and rear wheel, and bolted the driveshaft to the gearbox.

Now, when I turn the rear wheel, there's an orrible graunching noise - metal on metal - for about a quarter of a revolution of whatever it is that is revolving and making the noise. A bit like the noise you get when a brake pad rubs on a warped disc.

It's nothing to do with the brake shoes or wheel bearings as you can still hear/ feel it when the wheel is removed. The gearbox is also fine.

So (I think) it must either be something in the bevel box - or it's some part of the shaft rubbing against the swingarm.

I haven't touched the bevel box in over a year, and it didn't make the noise before (as far as I can remember) though it has been sitting for some of that time without any oil in it - maybe the crown wheel has gone rusty?

As regards the shaft/swingarm, I got the boxerman in leicester to remove and refit it for me when the swingarm was being powdercoated, as I don't have the means to compress the spring, which you have to do to release the circlip which retains the splined end bit. I can't imagine he's put it together wrong, or even that it would be possible to put it together with a bit sticking out so that it rubs on the swingarm.

Ideas??

Next step probably to pull bevel box off again and see if it makes the noise turning the output shaft by hand, though I'm pretty sure it wasn't...

 

[Rob Farmer]

Have you centered the swinging arm? If its a little off centre the uj will hit the side of the housing. This may also explain why it's only every quarter turn.

 

[SeanW]

yes - swingarm was cock-on centred. Tried moving a bit right and a bit left - didn't seem to make any difference to the noise

I will double check again though to make sure I've not done something stupid when reassembling...

Swingarm has had new bearings, but that shouldn't have affected anything...

 

[Kenny]

Just ensure the four stretch bolts have aligned the shaft to the gearbox correctly .... almost did the same myself ( laying on a cold/wet floor at my age )

 

[SeanW]

Just ensure the four stretch bolts have aligned the shaft to the gearbox correctly .... almost did the same myself ( laying on a cold/wet floor at my age )

...also checked that twice already

 

[Kenny]

Swingarm has had new bearings, but that shouldn't have affected anything...

Not sure if it would cause the noise but you did centralise the swingarm in the frame when you did the bearings ( probably teaching you to suck eggs here )

 

[DrFarkoff]

take the fd off and see if it still does it?

Yes then it's shaft / swingarm

No then it's final drive

 

[SeanW]

...got bev box off - no graunching going on in there.

It's definitely the driveshaft rubbing on the inside of the swingarm. I think the noise is coming from the bevel box end though, not the gearbox end

Theories...

It always made the noise but with oil in the swing arm it was much much quieter/ barely noticeable

I've somehow managed to squash the swing arm when I had in the vice to extract the old bearings

The driveshaft has become slightly bent (don't think this v likely)

Err...?

 

[DrFarkoff]

Take the swingarm back off and take it up to Phil Hawksley and have a look with him You didn;t drop an old shaft bolt in there did ya?

 

[SeanW]

spent some time at weekend taking it apart and putting back together repeatedly...

The noise is definitely affected by the adjusted position of the swingarm, as suggested. But the best I can do is fine tune it down to a very minimal scrape once per revolution.

But then, when I put the wheel back on and torque everything up the noise has become worse again.

It's not the gearbox flange or the UJ - there is masses of viewable clearance there.

One possibly important thing I didn't mention before - the UJ is a bit a notchy. Could that be causing the shaft to deflect more than it should do within the swingarm?

Will take it to Phil as suggested unless anyone has any other ideas?