BMW R51/3

[Martync]

Hi

I'm new to the Forum and totally new to owning a classic bike. I have wanted a BMW R51 for years and finally saw one and bought it.

I just wanted some tips as I'm used to Honda and the like. Are there good mechanics that can help with repairs to this model classic bike and any places where you can get parts?

The engine has a few oil leaks and I think needs a few new gaskets here and there. At this point I dont even know if the fixings are metric so do I need to buy new tools?

The bike needs a general tidy up and I havent the first clue as where or how to start, I intend to do it up bit by bit over a long period but right now just want to get it running good with no leaks and reliable.

I cant tell if the bike has had an unleaded conversion and obviously there's only unleaded available in Perth. What Oil does it need also for gear box, engine and hub etc...

Should I look for a 12v digital conversion, I do prefer electronic ignition

Thanks

[jono]

A good start would be yo come along to the club tuning day on May 16th, not only will you be able to access the collective knowledge but also relevant club tools to start you off. Start with the essential tasks first to make sure the bike runs safely. Then address the items you want to improve. Basic rule for electrics if iit sn't broke don't mess with it.

[wightman]

Yes, agree with Jono. Tuning day is a good place to start. Your engine oil should be changed every 6 months (2 litres) coz no oil filter. (20W/50W) Castrol GTX should do the job. The valve seats will probably not have had hardening, so just buy a $4 valvemaster 100ml at any servo and add 10ml for every 10l of petrol. The gearbox takes 80w/90W hypoid oil, up to the bottom of the threads and the final drive takes 250 ml of 80W/90W. You should try and start/ride the bike to warm up the oils before changing. Check for spark at both leads (you will need a 6V battery with charge) I personally would not mess with the standard equipment but you can put in a 12V system and electronic ignition. Vince, at Bassendean motorcycles can do it for you. You should try and meet Art Woldan, one of our members who has a 1953 (full hub) R51/3.

Enjoy

John

[art.woldan]

I have a 1954 R51/3 and the manual says the following about lubrication:
- Engine; all it says is engine oil as recommended by a BMW agent. I used to use Castrol GTX but now I use 15W50 semi-synthetic Rock Oil from Munich M/C's in Myaree. Munich says BMW used to recommend Rock Oil but now recommends a Castrol M/C oil because they're affiliated with Castrol somehow, but I've kept on using Rock Oil. The engine only required a rebuild at 82,000 miles (not km) so the oil must have been OK considering that 1950's oils would have caused more rapid wear at that time.
- Gearbox; the manual says engine oil as well, and I use Castrol GTX 20W50. This isn't as extraordinary as it seems because I have a Mobil Oil viscosity chart that says 50W crankcase oil has the same viscosity as 90W gear oil. When the gearbox is cold shifting must be deliberate but once it warms up it's good. If shifting is still difficult when the gearbox is warm and it's in good condition it's because the clutch isn't releasing properly and the screw on the back of the gearbox must be screwed in slightly.
- Rear Drive; the manual says SAE 90 lubricating oil. However, I have info that hypoid oil shouldn't be used because it can affect the seals. I haven't found any 90W non-hypoid gear oil so I use straight 50W non-hypoid engine oil that I purchase at a Harley shop. I believe some Ducatis use it as well. As mentioned, 50W engine oil is equivalent to 90W gear oil.
My gearbox and rear drive have never been worked on so these oils must be satisfactory.
- Drive Shaft Universal; grease occasionally. A trap for young players is that the cover has a left hand thread, opposite to a normal thread, so the drive shaft rotation doesn't loosen it.
- Forks; I use 5W Castrol fork oil.
- Wheel Bearings; I use Castrol HTB grease.

A well known problem with all pre-69 BMW's is debris filling up the crankshaft slingers. If this occurs debris can enter the big ends, and cleaning the slingers requires an engine strip, unfortunately, and there's no way to inspect the slingers without pulling the engine to bits. Thorsten Friz located next to Munich can do this work. On your bike if it's documented that the slingers were cleaned not too many km's ago you're fortunate.

Art Woldan

[art.woldan]

A lube point the manual doesn't mention is the rear drive splines. (This is more important on the Post '69 airheads.) I use Honda Moly 60 Paste because I read it contains a higher percentage of molybdenum disulfide than any other moly grease.
Art Woldan