Gearbox noise

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m0rt
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Gearbox noise

Postby m0rt » Wed Jun 20, 2018 6:42 pm

Hi all.

So I have recently aquired anoth 92 R80 RT, which runs well apart from revs not reducing when warmer (bean can I assume).

However, there is a noise coming from the gearbox I just picked up when it is in neutral (can't hear when riding).

It isn't a rattle, not a rumble, it is cyclical and stays with engine revolutions but not as fast, maybe 4-6x slower. Pull the clutch in and it goes.

Trying to work out how best to describe it, not quite a whirr, sounds a little bit like a (small) pepper mill being turned but not grumbly. Just like lots of little gears turning.

I appreciate how rough this is but... any comments?
Last edited by m0rt on Wed Jun 20, 2018 7:31 pm, edited 2 times in total.

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Re: Gearbox noise

Postby m0rt » Wed Jun 20, 2018 6:52 pm

Oh - I should just point out that I 'pinpointed' the noise using a wooden hammer shaft, from the right hand side. It is most audible three inches back from the front edge of the gearbox, if that is any help whatsoever.

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Re: Gearbox noise

Postby Jon K » Wed Jun 20, 2018 7:36 pm

What makes you think the revs hanging when warm is the ignition sender unit? I may be the least knowledgeable person on here but I would have thought that was more likely to be a minor carb problem, slide sticking or throttle linkage not returning maybe.

Odd noises? Been there and got too fat for the t-shirt. They’ll drive you bonkers if you let them.

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Re: Gearbox noise

Postby varley55 » Wed Jun 20, 2018 8:05 pm

Noise sounds like it’s coming from the layshaft, maybe a bearing on the way out. When you pul in the clutch, the layshaft stops spinning.

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Re: Gearbox noise

Postby boxerman » Wed Jun 20, 2018 8:07 pm

Noise is almost certainly just cltch rattle. As a rule of thumb if it stops when the clutch is pulled don't worry about it.
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m0rt
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Re: Gearbox noise

Postby m0rt » Wed Jun 20, 2018 9:34 pm

Just did some further testing. It makes the same noise if I coast when pulling the clutch in.

So something turning in the gearbox makes this noise?

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Re: Gearbox noise

Postby andyb » Wed Jun 20, 2018 10:38 pm

If clutch rattle, balancing the carbs and raising the tickover speed a little helps.

Or earplugs

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Rob Frankhamr
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Re: Gearbox noise

Postby Rob Frankhamr » Thu Jun 21, 2018 12:35 am

Just did some further testing. It makes the same noise if I coast when pulling the clutch in.

So something turning in the gearbox makes this noise?


Sounds like a gearbox bearing I'm afraid...

Rob
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m0rt
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Re: Gearbox noise

Postby m0rt » Thu Jun 21, 2018 8:56 am

Just did some further testing. It makes the same noise if I coast when pulling the clutch in.

So something turning in the gearbox makes this noise?


Sounds like a gearbox bearing I'm afraid...

Rob
Yeah. The reason why I didn't immediately jump to that conclusion is that it is not like a bearing sound I would expect. Meh.

Previous owner had gearbox apart in the past over a nylon bush issue. Seems to know what he was doing. I think he used to be a member of this Parish. The bike appears to been well maintained and runs very well - it is a high mileage machine around 123K.


Anyway - I need a plan of attack.

Anyone know of a repuatble gearbox rebuilder? I am based in North Wales, so I guess that It will be a postal job. Or is it a case of just getting an exchange recon unit from Motorworks?

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Re: Gearbox noise

Postby george baker » Thu Jun 21, 2018 9:19 am

Hi
some general motorcycle places dont rebuild during the summer DAMHIK , although gearbox specialists will.

If you fit a used exchange box and it has a problem then Motorwords will exchange it BUT it means double the work and postage

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m0rt
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Re: Gearbox noise

Postby m0rt » Thu Jun 21, 2018 9:27 am

Wouldn't go for just a used exchange. I would rather get a recon one.

Or get a proven airhead box rebuilder to do it.

Phil - regarding the clutch chatter - I want it to be that but the noise is a whirring sound, that comes in and out, slower than the engine but in sync. So I suppose this ties up with a bearing because of how many revolutions the layshaft will do to one revolution of the bearings in the race.

Obviously I appreciate this is all complete and utter speculation based on my rough pepper mill comment. :) For all I know it may have always made this noise. However, I haven't noticed this noise before on previous airhead.

I mean it may do thousands of miles like this. It may do 50.

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Re: Gearbox noise

Postby windmill john » Thu Jun 21, 2018 9:40 am

I haven't noticed this noise before on previous airhead.

Don't make me say it m0rt!!!
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Re: Gearbox noise

Postby Rob Frankhamr » Thu Jun 21, 2018 9:50 am

It's as likely to be the input shaft as the layshaft... both shafts rotate when the clutch is engaged but not when it is released. Doesn't really matter too much, at this point the only real option is a reconditioned box whether you buy a box or recondition the original.

Rob
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Re: Gearbox noise

Postby m0rt » Thu Jun 21, 2018 10:00 am

I haven't noticed this noise before on previous airhead.

Don't make me say it m0rt!!!
Wouldn't dream of it, John. :D

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Re: Gearbox noise

Postby m0rt » Thu Jun 21, 2018 10:01 am

It's as likely to be the input shaft as the layshaft... both shafts rotate when the clutch is engaged but not when it is released. Doesn't really matter too much, at this point the only real option is a reconditioned box whether you buy a box or recondition the original.

Rob
Yep.

So need pointing in the right direction for a good box builder.

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Mark Esposito
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Re: Gearbox noise

Postby Mark Esposito » Thu Jun 21, 2018 12:34 pm

Roger Bennett in Huddersfield has a good reputation over the forums, infact there is another current thread with a member who has a gearbox with him at the moment.

https://r.tapatalk.com/shareLink?url=ht ... are_type=t

Clutch failure R90S


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Re: Gearbox noise

Postby m0rt » Thu Jun 21, 2018 1:04 pm

Thanks for the time and information, guys.


Just for reference, here is the noise:

https://youtu.be/2FgIX3UOKeM

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Re: Gearbox noise

Postby adrian967 » Thu Jun 21, 2018 1:40 pm

My gearbox is indeed with Roger as we speak....took it Tuesday and he promised it back today..I opted to have it cleaned so another couple of days.
He has gearboxes all over his workshop and loads of other stuff too.

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Re: Gearbox noise

Postby ts » Thu Jun 21, 2018 8:24 pm

I happened to post a similar query - with the same title - somewhere else not long ago.

Link to video with my gearbox noise: https://youtu.be/dNenhDfQYXw

- which can be heard only when the gearbox is warm, and in neutral. It goes away when I pull the clutch lever. I had the gearbox apart and replaced rough bearings on the output shaft not long ago. I was wondering if the noise that now can be heard could be due to a worn front bearing on the input shaft, and was told not to worry, and use thicker oil (75-140 muiti grade), or get better earplugs. Which should be sound advice if it indeed is the front input shaft bearing, which is a roller pin bearing that usually doesn't break apart.

(Edited for clarity)
Last edited by ts on Thu Jun 21, 2018 11:29 pm, edited 2 times in total.
ts
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m0rt
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Re: Gearbox noise

Postby m0rt » Thu Jun 21, 2018 11:09 pm

I happened to post a similar query - with the same title - somewhere else not long ago.

Link to video with my gearbox noise: https://youtu.be/dNenhDfQYXw

- which can be heard only when the gearbox is warm, and in neutral. It goes away when I pull the clutch lever. I had the gearbox apart and replaced rough bearings on the output shaft not long ago. I was wondering if this could be due to a worn front bearing on the input shaft, and was told not to worry, and use thicker oil (75-140 muiti grade), or get better earplugs. Which should be sound advice if it indeed is the front input shaft bearing, which is a roller pin bearing that usually doesn't break apart.
Interesting you say that.

The previous owner got in touch, and after listening to the video said the 'rhythmic groaning' was familiar and he just put it down to a higher mileage box. So that is fairly reassuring. It means it that there probably isn't real danger of imminent change.

I also found the cause of the slightly higher revs sometimes. The left carb return is a little 'slow'. I'll pick up some new springs for that.

Tell you what though, Hagon shocks and progressive springs a spritely airhead make.

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Re: Gearbox noise

Postby ts » Thu Jun 21, 2018 11:34 pm

The previous owner got in touch, and after listening to the video said the 'rhythmic groaning' was familiar and he just put it down to a higher mileage box. So that is fairly reassuring. It means it that there probably isn't real danger of imminent change.

I assume you have checked the magnet on the drain plug for sharp metal fragments? That would be a strong indicator of imminent bearing failure. Or drained oil with a metal-flake shimmering appearance.
ts
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m0rt
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Re: Gearbox noise

Postby m0rt » Thu Jun 21, 2018 11:39 pm

Not yet.

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Re: Gearbox noise

Postby Mike D » Fri Jun 22, 2018 12:48 pm

Mike Overy (Overland & Classics) has a good reputation for gearboxes (well all things BMW really) he is in the Vale of Belvoir.

Mike

m0rt
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Re: Gearbox noise

Postby m0rt » Fri Jun 22, 2018 1:13 pm

Funnily enough - I spoke to him this morning.

:)

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Re: Gearbox noise

Postby Mike D » Fri Jun 22, 2018 5:43 pm

What did he have to say?

Mike


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