All sortsa' oils

[lukasgrech]

It is leaking, quite slowly, but it is noticeable

[lukasgrech]

No problems, only opportunities...

So after approx 150miles of riding this weekend, I had a look at the oil levels again:

Gearbox has not lost any oil - good.

Driveshaft is practically dry again (stripped thread/highly porous rubber boot spewing oil) - bad

Bevel box oil, reduced to what it was before I drained and re-filled, I'd say it's lost about half the oil again - bad?

1. What damage am I risking, riding the bike with such low driveshaft and bevel box oil levels?

2. The driveshaft leaks are pretty obvious, but the bevel box? Drain plug is installed correctly, and I don't see how it could leak that much oil all the way up the driveshaft through the boot, even if a gasket or seal had blown

[georgesgiralt]

Hello !
Remove he rear wheel and see if the drum is wet or not. If not, maybe the rear drive is leaking oil into the swing arm where it is lost by the leaks you already noticed ....
If the rear drive oil is transferred into the swing arm, you're not lucky because this lip seal is not easy to change without special tooling. (from BMW or custom made.)

[lukasgrech]

Yep I feared that's what might be happening. I'll have to do some disassembling and investigate further.

Thanks!

[drew857]

My thought exactly... I am lucky enough to have access to motor oil from my fiends garage and I have no leak problems after 50K on a 1982 R65T. Modern oil I believe is far superior but i would change more often just for peace of mind, oh and I like getting my hands dirty.

[montmil]

If you are noticing, and can confirm, oil loss from the final drive, there are a couple items to check:

1)  The rear brake cam should have a couple small o-rings that seal the cam-to-case contact. The brake cam is steel and there is no bearing of any kind for the shaft to bear on; just the aluminum final drive case. Look for weeps n' seeps at the rear brake arm attach location.

2)  Beneath the Cardan cover -the casting where the drive splines pass through- is a large oil seal that bears on the spline shaft. If it has become overheated, split or abused with dirty lube, it can leak into the final drive and then out the bottom.

Both items are fairly easy to check and/or replace.

Chasing drips can be challenging. Dusting with baby powder can help... sometimes.

[lukasgrech]

So I did a very thorough job of chasing the oil drips and I can confirm that the only leaks are from the torn up rubber boot, and from the driveshaft drain.

The bevel box has stopped leaking and the oil seems to have settled at that low level. To me, this rules out any possible leakages from around the bevel box (drain/seals etc.) as otherwise it would continue leaking until it was empty.

[Barry]

The bevel box will get by with less than the normal level but how much less do you have ?  You could drain it out, measure the volume and put it back again.

Remembering this is a 79, the potential brake cam leakage is not applicable. To explain for Lukas, on the 81- on models the bore for the brake cam shaft is open to the final drive oil so needs O ring seals on the shaft to keep the oil in and they can still leak. BMW increased the number of O rings from 2 to 4 in an attempt to improve sealing.

On the 78 - 80 models it's a straight through closed bore with no possibility of final drive oil getting to the shaft which is only lubricated with grease on assembly. There is a felt washer on the inside to keep the grease in and that's it.

If you have the rear wheel off for any reason it's worth removing the brake cam to clean up and lubricate the shaft as it's not a scheduled service item and so  may never have been done from new. Mine hadn't.

[lukasgrech]

So I finally got around to give the bike some attention - toothbrush and elbow grease cleaning, I wanted to keep water distribution to a minimum.

I measured the bevel box oil, and there was about 100cc in it, it has stayed pretty stable at this level for the past few rides, I did a visual check from the filler plug after a few of the rides, and the level didn't seem to be moving. I refilled with about 150cc, cleaned up the bevel box and dusted with baby powder so that any leaks will hopefully be visible after some use.

I will eventually come to a point where I'll have to remove the driveshaft, swingarm, rear wheel etc, in order to replace the rubber boot. At that point I intend on giving the whole assembly a bit of an overhaul - lube the brake cam shaft, repair the driveshaft oil drain (helicoil?) and make sure everything is sealed up. Until then, I will have to make do with the occasional oil drip cleanup, and avoid riding too much in the rain.. not such an easy task in the UK!

[arvo92]

Can anybody explain the bevel box seal replacement procedure please!

Mine is leaking bad after changing the bevel box to a new used one as my splines were totaled. Reducing the volume of oil did eliminate the drips when bike is stationary but when I get on the road and rev hard (contrary to Steve Hawkins's reccommendation), the whole tire will be sprayed. Easy riding will not do the trick.

Leak comes from the centre of the bevel box output seal (the large diameter one) and finds its way down between the bevel box and wheel.

[nhmaf]

The large seal around the drive spline to the rear wheel that Arvo has a problem with is considerably easier to replace than the seal which is on the input (driveshaft) end of the cardan drive unit.   Somewhere here we had a thread with pics on this.    Maybe Monte wrote it up - it is in this thread -
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1394488408/12#12

Along with the seal around the output splines, you should/must also replace the thin paper gasket that goes between the inner cover and the main housing of the cardan drive.   monte's write up and pics in this thread should help you through it.   If you don't drink beer or other beverages from aluminum cans, you could also just get a good length of electrical tape or duct tape to wrap several times around the output splines to protect the inner surface of the output seal as you slide it into position.

[Bob_Roller]

One thing that isn't in Monti's write up, is there are two small threaded holes in the cover, they are for a small bolt / screw to thread into, when the bolt contacts the case, it starts pushing the cover off .

You can see these in the third picture, but I beleive the R65 cover  has these bolts in a bit not in tabs on the edge .

You ca nheat the cover up and cool the crown gear and it makes for an easier reassembly .

Also replace the two o-rings 0n the brake cam shaft .

[arvo92]

Thanks for the link. That info is useful. It seemed a far more complex chore before knowing these tips. I do have all the required tools/seals to get the job done but I have to add this into the "to do list".

I got my bike MOT-d and registered 3 days ago and after lots of years she is back on the road. I really do not want to take any jobs on at the moment as riding her is a blessing at the moment. She is my daily commuter to work and she is running strong with a occasional period I can cope with that for a week or two I guess.

[drew857]

Hi there, noticed you are in the UK - Try B&Q 20/50 just over £10 and a quality oil, my friend a Chemist at BP grangemouth checked it out and thinks it has all the properties requires for older bikes esspecially Air-cooled twins...

You should be able to tell if the oil is from the gearbox or engine by the difference in smell with gear oil usually having a distinctive odour.  Likely culprit is the neutral switch visible in your pic.

Whether you top up or change the oil don't fill above half way between min and max marks on the dipstick. This is to maintain some air space in the sump which will minimise oil loss via the engine breather. This is a generally accepted policy across all airheads and is particularly applicable to a 79 as it has a slightly shallow sump than the later models.

If you are going to top up I wouldn't worry too much about what to put in. What oil have you got to hand if any ? I'm a fan of 10w40 but 10w 30 is definitely too thin for year round use even in our climate.

The oil chart in the riders handbook gives BMW's view in 1979 which is still going to be fine as far as protecting the engine. They did however  through a series of service bulletins provide revised guidance over the years as oil specifications changed. Generally there was a move to accept the use of thinner oils like 10W40 at higher ambient temperatures. This chart issued in 1995 is the latest one definitely applicable to airheads.

[Barry]

Try B&Q 20/50 just over £10 and a quality oil, my friend a Chemist at BP grangemouth checked it out and thinks it has all the properties requires for older bikes esspecially Air-cooled twins...

It would be interesting to know who makes their oil.  There are only so many oil companies that produce lubricant oil. It's a similar senario to "BMW oil" which used to be Spectro and is now Castrol. I suspect you can write a specification for oil and have any oil company make it.