R100RS (Motorsport) Oil Leak at Gearbox

[IRE100]

Hi All,

New to the forum so I hope this post is ok. Im basically looking to gauge whether a price I have on an R100RS Motorsport is reasonable (I’m looking to buy).

I have been looking to buy an R100RS Motorsport for a few years on and off and never found one in budget. The bike would be my first airhead but the R100RS in general has been my favourite bike for a long time and if I managed to get my hands on one I can see myself passing it onto the kids some day

My problem/question is. I have found a private collector with an R100RS motorsport in Germany through family with 70k kilometres on the clock who is willing to sell for around 5k which could be my only chance to garage one of these amazing machines. However at that price there as you may imagine there is an oil leak from the gearbox rear main seal but he assures everything else is in good order.

The seller assumes about 2k to get the oil leak sorted with new clutch while the mechanic is in there.

Whats people thoughts on this? Is the 2k bill accurate? Is the 5k asking price fair? I have other bikes and am comfortable working on bikes to a certain degree. Could rear main shaft seal be done in a home garage by a job over winter?

Any feedback would be amazing thanks guys.

[Rob Frankham]

Hmmm,

Call me Mr Suspicious but I would want to know why the owner thinks there is a leak from the gearbox rear seal... The output shaft of the gearbox is in the volume enclosed by the drive shaft tunnel and the rubber swing arm/gearbox boot so a leak here isn't readily apparent. It would normally present as an increase in the volume of oil in the drive shaft void… but that can be down to a number of things.

That being said, assuming his assessment of the bike is accurate, then I will try to give my opinion on the bike.

a) I don’t know where you are and what currency you are working in. Being in the UK, I will use GB£ but if you work in Euros or US$ (or anything else for that matter) it will be necessary to convert.

b) I don’t know what you want the bike for. If it’s just for riding, then some of the things I will say aren’t relevant but if you are looking at it as an investment, then there are a number of things it would be wise to be sure of before committing yourself.

So, if you’re, looking for an investment… the value of the ‘RS isn’t particularly high at the moment. The ‘Motorsport’ finish does help but only if the provenance is good. Is it a bike that was designated as a motorsport on the production line or is it just a normal ‘RS that has been refinished in ‘motorsport’ colours? It’s not that easy to find out.

It’s worth commenting that the Motorsport special edition is a finish. The bike is mechanically no different to a contemporary standard ‘RS and that, according to BMW documentation only 200 examples were ever built for the ’78 model year. They did not carry the Motorsport roundel (which was only used on cars) and they featured a blue seat.

Needless to say, the engine and frame numbers should match and putting the frame number into one of the parts lists (REALOEM or MAXBMW) should confirm whether the bike actually came with the Motorsport finish.

Another point as whether the paint is original or resprayed.

All of these points are very important if you are looking for a motorsport as an investment and the best price will go to an ‘unmolested’ bike with original paint. If all of these conditions are met, then I would say that 5k (GB£ remember) is quite a good price.

If, on the other hand, you’re looking for a bike to ride, then most of the points above aren’t so important (but one does have to ask why you insist on a motorsport which is likely to be overpriced compared to other contemporary RSs).

5k is towards the top limit I would want to pay for a ’78 RS at the moment and it would have to be a good bike to command that.
Moving on now to the gearbox leak… assuming the owners assessment is correct and there are no other issues, the job is relatively simple. A reasonably competent amateur wrench could do it for less than £50.00… In a garage, it’s should cost no more than - say - £300.00. It’s a job that can be done without removing the gearbox so it’s a moot point whether you need to do the clutch at the same time. I would expect the friction plate to have been changed in 70,000 km… if it hasn’t then I would change it. If it’s been changed, it would depend on how many miles it has done.

If you’re replacing the pressure plate, then I’d recommend that the spring is replaced as well. You might want to think about a heavy duty spring. Price for a clutch… less than £200 done yourself, probably no more than £500 by a garage.

Buying a second hand vehicle is always a lottery but, all things being equal (and with due regard to the ‘currency’ thing), if you’re happy with the deal then I can’t see a problem… but do be careful…. overseas car deals are a regular and fairly safe scam (for the scammer that is) so get all of the guarantees you can.

Rob

[IRE100]

Hi Rob, thanks so much for taking the time for the comprehensive reply! I will try clear a few initial things up.

I am in Ireland and the bike is in northern Germany so the currency is in Eur apologies for not stating that.

I have yet to see evidence of the frame numbers but the bike is 2 owners from new and the blue seat is present. Paint is very good apart from the seat cowl where luggage strappings seems to have caused chipping.

It is also a kickstart which I believe is inline with 78 motorsport models spec.

The current owner is a collector, I found the bike in person and asked if he would be open to selling it as mentioned I have been chasing one for quite some time. This RS was one of several old airheads he had and each was a limited run of some kind.

I will have to query his reckoning on the rear main seal being the culprit as you mention it’s perhaps not easy to diagnose without a certain amount of disassembly which I am not certain was done.

With regards to my motivations and intended use. I do intend to use the bike certainly it won’t be left in the garage but it will very much be a weekend toy. I fully agree that a standard RS is no different and that I can only put down to the illogical side of my brain loving that red nose and the confusion about how many there are, why they were built, the stories about them being intended for British police at some point etc. Ever since I learned about these motorsport models they have intrigued me even though they are perhaps a marketing exercise!

With all that said I am comforted somewhat by your take on the technical skill required to handle the job as a hobbyist. My main worry comes from the fact that in Ireland there is very little support for these old airheads as we don’t have a huge amount and I have found only 1 or two people even willing to work on them. I would hope to be able to carry out any necessary works myself but if I needed a mechanic as a catch-net it would be slim pickings here by the looks of things.

Im due a call with the seller on Monday to try and close out some more questions so will certainly follow up on frame numbers and his assessment of the oil leak! Thanks again Rob!

[Rob Frankham]

I confess that I don't know the reason for the 'Motorsport' but I suspect the link to the British Police is fanciful. I have always thought that it was a marketing ploy to capitalise on the BMW car racing team which used the Motorsport name. As far as I'm aware, no british police force contracted R100RS models for patrol use (there were the odd ones for 'specialist' use) and, in the late 70s, most UK forces were still trying to use British machines (mainly for political reasons). I wouldn't go so far as to say that it isn't possible (stranger things did happen) but I think it is most unlikely.

In my experience, most jobs on an airhead can be tackled by reasonably competent amateur but you may need some special tools. For example, to replace the gearbox oil seal (should it be necessary) you will need the following:

1) A special puller for the gearbox output flange (This is an unkeyed morse taper and is (or should be) very tight. Using an unsuitable puller is very likely to result in damage and/or personal injury... don't be tempted!)

2) A 27mm socket with thin walls to suit the rear swing arm pivot locknuts.

3) A Bi-hex 10mm wrench with thin walls to fit the gearbox output flange bolts.

The UK BMW owners club has a most of the special tools for hire. There is an Irish section so I would assume that they'll send them to Ireland...

A good manual is important but all manuals have anomalies so if you are planning anything which is pushing your comfort zone, it's a very good idea to ask on the forums... There is always a large number of people who have done it before. Spares can be sources from the UK fairly easily and I will mention 'Motorworks', 'MotoBins' and 'James Sherlock' as competent and reasonable sources. Can't help with any sources or mechanics in Ireland but I'm sure you'll find some if you ask around.

Finally, on the kickstart... BMW stopped fitting a kickstart as standard to machines (other than the 'GS series) around 1975 but they were an option on all machines right up into the Monoshock era. Many of the first police spec machines were specified with them in the first few years but they were found to be unnecessary. In fact, I'd go so far as to say that they were tolerably useless on any bike with the 5 speed box ('74 and later). The gearing ratio isn't good and one gets the feeling that they were designed as an afterthought. If everything else is good, they can be used to start the bike but if anything is off whack (and when else would you need to use a kickstart on a bike with a competent starter motor), they seldom work. That being said, although they weren't in the standard spec, they aren't a problem because so many bikes of the era were specified with them.

I will also mention a couple of other forums that are worth subscribing to:

BM Bikes - https://www.bmbikes.org.uk/Forum/ucp.php?mode=login - UK Based
BMW Motorcycle Owners Club UK - https://forum.bmw-club.org.uk/- UK Based

Anyway, good luck and if I can help in any way with advice & etc. please don't hesitate to give me a call.

Oh, and FWIW all thinghs being equal, €5,000 is probably a pretty reasonable price...

Rob

[IRE100]

Thanks so much Rob you are a gent! I am very excited about the prospect of owning one of these legendary bikes so I hope it all goes well! Im certainly feeling more confident about the prospect given your feedback, info and links.

If all goes well and I seal the deal next week I will drop a note here!

Thanks again.