Bevel Box Oil Leak??

[dr nosh]

Went for a 150 mile ride yesterday on the 80ST - First sunny, dry summer Sunday this year, or thats what it felt like

Anyway, found spots of oil on the rear rim coming out from the rear brake hub.

Stripped down and found:

NO oil around the drive output hub -

Oil is coming from the brake cam shaft.

Removed shaft and O rings look ok but must be worn.

BUT

Oil came out of the shaft opening

(3000 miles since oil change and is golden - a good sign)

So, have I overfilled the bevel box?

(Its now stopped and have lost probably about 30 cc).

Have I missed anything else?

Checked gearbox oil level - Perfect - Just touches threads when level plug removed.

No other oil leaks anywhere.

Sequence of re-assembly of brake cam - Felt washer on the outside, thrust washer on the inside ?

Check level of bevel box

Thanks

 

[Rob Farmer]

Theres a steel tube that the shaft sits in. Have a look at that to see if it's rusted through. Moisture can get trapped by the O rings on the shaft and then just sits there rotting the tube.

The tube is part number 25 in the picture

 

[dr nosh]

Thanks Rob.

Well I can't see a steel tube.

I can see a 2 piece bronze tube - 1 piece pressed in the outer casing and 1 piece pressed in the inner cover.
Looking in here I can see into the bevel box and can see the end of the M6 oil level screw.
The oil level has actually settled to the bottom edge of the bronze bush.

There appears to be a part listed in Motorworks p/n TRA01699 Rear brake cam spindle bush in bevelbox D=15.8x84.5 ( Mono / G/S / ST )
This is a one piece part.

Are you suggesting that there should be NO oil able to come out when the brake cam spindle is removed. ?

With the Motorworks part I could understand this. Also, this would put less pressure on the shaft O rings, as with the current arrangement its just the 2 O rings verses the oil in the bevel box.

 

[jimish]

I've just been thru' this on my '83 R80ST - after an oil change the rear brake stopped working on a ride. Oil all over the shoes.

I had filled until oil dribbled out of the filler hole at the back of the bevel box, which is what Haynes say to do, but when I drained it out there was 300ml of it (and I'd already lost some don't forget) Haynes also say the capacity of the bevel box is 250ml (or cc's, same thing).
I refilled with 250ml and after about 300 miles there is no leak.

I would like to know what BMW say the capacity should be. Anybody got a handbook?

There is no steel shaft for the brake shaft on my ST, just the two bronze tubes, outer and inner. So the brake shaft gets lubed in use, hence the o rings. There should be 4 o rings, 2 for the outer part & 2 for the inner, and yes, felt washer outside (Stops road shit getting in), plain steel washer inside.

 

[Rob Farmer]

I would like to know what BMW say the capacity should be. Anybody got a handbook?

Bronze tubes?? I'd have put money on it being a steel tube. I'm probably getting confused with the Paralever unit. I have a mono bevel box that was stripped a while back. Should be in the garage somewhere.

This is from the BMW technicians workshop manual. The ST is the same. Differences between the two models tended to be issued as an ST supplement rather than a complete manual. Heres the riders manual supplement for the ST http://www.2zars.com/r80st.pdf I had a link to the ST workshop supplement but I'm damned if I can find it now. G/s Riders manual here http://www.restat.de/r80gs/gs_om/index.htm They all consistently show 0.35 litres for the final drive.

 

[John Roberts]

I may be speaking out of turn here, but I did a job for somebody a while back who was converting a drum to a disc brake setup on his Airhead, he wanted me to remove the two BRONZE bushes in the bevel housing and replace them with a couple of stainless bungs. Sorry, but I can't remember any more details, all he wanted from me were the bungs, but the bushes were on my bench until a few weeks ago, and they really were bronze.

Having said all that, isn't it unusual to have a steel shaft running in a steel bush??

 

[jimish]

Thanks for all that info Rob. Very useful. It doesn't surprise me that Haynes got it wrong. So I had better fill mine up with 350ml and see if it leaks then!

I've never had a paralever bevel box apart so I can't comment there, but I've checked my G/S (it's in bits for a resto) and that has 2 bronze bushes just like the ST.

 

[dr nosh]

Well looks like I ordered the wrong O rings.
Motorworks delivered today, ordered yesterday.

BRA57605 are a thin section O ring and might be for a Paralever perhaps.

BRA06328 is the thicker section O ring looking more like what is currently fitted.

Motorworks list 3 required, but clearly 4 are required.

I've also ordered TRA01699, bush 1 piece 15.8 dia x 84.5.

In theory this would 'seal' the opening to the bevel box thereby preventing oil from escaping past the O rings.
Might be a bit of a job to press in whilst the box is fitted, also, would need to press both pieces of the existing bush out - without dropping into the box.
I suspect that will have to wait for a time when I'm rebuilding it again.

So the best current solution would seem to be ;

1. Reduce oil level in box. BMW recommend 350cc, MAXIMUM, up to level plug. If there is alrady some residual oil in at an oil change, that could account for perhaps 20 cc, meaning you could then have 370 cc in. I have probably lost 40 + cc.The oil has settled at the lower edge of the bronze bush (bike on centre stand, front wheel touching floor).
This would get me to about 300 cc.

Will reassemble with new O rings (tomorrow I hope), and this reduced quantity of oil.

Interestingly, I 've done 3500 since a rebuild and absolutely fine until now.

Still its given me an opportunity to get out and ride my Ariel Red Hunter

 

[jimish]

Don't know how you've got on with this but I checked the breather/filler today and it was nearly blocked. Try blowing through it. I suppose that as the bevel box warms up the oil pressurises and if it can't breathe out of the breather it forces oil out of the brake shaft.
Cleaned it out with some wire and see how that goes.

 

[dr nosh]

Thanks jimish.

There was another thread on this very subject by england-kev - blocked breather.


Just getting some rays in the south of Spain right now, but is on the list of jobs to do on return to blighty.

 

[tuftywhite]

Dear Dr.

I've been through this with my g/s.

Mr Arkright of this parish put me on to it.

The final solution was to take the drive to Steve Scriminger (http://scriminger.co.uk). He expertly, quickly and extremely reasonably, fitted a sleeve for the spindle to go through in the oily bit.

Job done, no more leaks, ended 12 months of repeated shoe and hub cleaning after each ride, not to mention the oily patch on the garage floor.

Hope this helps.

Tufty

 

[dr nosh]

Might have ago at replacing the bush over the xmas break.

What do you think my chances are of doing this on the bike without removing the final drive?

This is what I thought:

Drain oil.
Warm up drive housing - gently - using hot air gun.
Use a 8" G cramp to push the new one piece bush into place, whilst pushing out the 2 single bushes into a piece of tube.
Re-fill oil etc.
Ride.

If all else fails will have to remove final drive and get over to Sleaford.

Seasons Greetings to all Airheaders!

 

[Rob Farmer]

Here's a picture of a G/S bevel box with the helical gear removed. The tubes been taken out of this one. But you can see it just pushes into the outer and inner covers.

You should be able to remove the inner cover and replace the tube with the bevel box on the drive shaft but it may be very tight. I made a mandrel that fitted inside the tube with a small lip to sit on the shoulder of the tube, this allowed the tube to be knocked out without distorting the edges.

 

[Beemerboff]

Not all G/S final drives have the tube- mine has two bronze bushes and the shaft with four O rings ( or two on the 'Bins site or three in the 'works site) and the centre of the brake shaft running in the bevel gear oil.

The O rings supplied by 'bins are slightly smaller than the ones coming off, but that may just be because the old ones have swollen a bit.

But the idea of having a continuous tube with the brake cam rod separate from the oil on the bevel drive seems a better solution - is it just a case of replacing the two bushes with the long tube supplied by Motorworks, or is there more too it than that?

 

[dr nosh]

Well I am hoping that I can get the 2 old bushes out and press the new one piece in with the FD still on the bike.

I'm sure this arrangement will be more oil tight as oil cannot enter the tube and then leak past the O rings.

Will need to add lubing of the brake shaft to the service list.

 

[ianboydsnr]

Had a look at my spare bevel box today, mine is an early one, there seems to be only one brass bush in the front cover, there is no evidence of one in the rear cover, and it is the same size as the bushed front,
I have removed the bush, I plan on fitting the long tube, once I find my adjustable reamer,

I must check the one on the bike, that probably needs done as well,

Having had the oil leak on the brake shoes on my old R65, I don't want to go there again

 

[solidstate100]

Epic thread revival!