Oil Pressure Specifications

[clmedlin]

What are the BMW specifications for oil pressure on a 1975 r90/6? There is a lot of varying data being posted (I.e. Snowbum 14-29 psi / Brooks 85 psi). I am unable to find a BMW answer and am very curious what “right” should be for my bike.

Background - I just completed the rebuild of a r90/6 barn find project and am getting ready to do my 600 mile service. I want to be confident that the bike is performing as it should be.

Thanks in advance for the assistance.

 

[20774]

Seems like those numbers you list should be for some condition...I suspect that the 85 psi might be instantaneous cold start up. Anyway, my Haynes lists for oil temp at 176 defF, the pressure at 800 RPM is 14.5-29 psi (Snowbum's numbers) and at 4000 RPM is 58-72.5 psi. The oil pressure light comes on below 3-7.3 psi.

I'm sure you'll be fine.

 

[RPGR90s]

'74 R90s with 144k that I've owned since 1980 with crank, lower end being totally untouched. I installed a high quality oil pressure gauge last summer for curiosity and noted after a 10 mile warm-up a consistent 65psi at 4,000 rpm. If your stock oil pressure light doesn't come on at idle, you should have nothing to worry about.

 

[clmedlin]

Thank you!

 

[robsryder]

I am not 100% certain that I am recalling things completely correctly. There was a feller, named Fred Tausch, that had many, many miles on his R60/5 (around 640 kmiles) prior to his passing some years back. Fred ran an oil pressure gauge on his bike. I think that there was some discussion about his use of a VW beetle-type of oil sender that has dual outputs. A brief bit of googling reveals such a dual output oil pressure sender -

https://www.partsgeek.com/hcbdmtz-volkswagen-beetle-oil-pressure-sender.html?gb=pp&cid=28884375&aid=4168799374&kid=1100003048986

Note: the above VW oil sender has threads that are m10 x1.0 which is NOT the correct size for an airhead. The correct size is m12 x1.5 (from EME website).

Oil Pressure Switch for BMW R Airhead ; 61 31 1 243 414

Oil pressure switch for BMW R Airheads ; 61 31 1 243 414, 61 31 1 354 274. Ensures accurate and consistent oil pressure signal to dashboard instrumentation.

www.euromotoelectrics.com

A past discussion about adding an oil pressure gauge to an airhead is found on the MOA forum -

Oil pressure gauge for airhead?

Asked this as an oh-by-the-way in another thread, but so that folks not following that one will see it: Does anyone sell oil pressure gauges for airheads? I sure would like to be able to monitor oil pressure on the go, rather than relying on the idiot lamp. Thanks - Brian

forums.bmwmoa.org

 

[20774]

According to Snowbum, the threads are typically M12 x 1.5 however early Airheads had 3/8 NPT threads.

 

[robsryder]

In high school (early 70s) I had an old British car. I did not know about Whitworth. I knew metric (from small Honda dirt bike) and 'merican. I found anything "close" could be made to fit (ONCE) through the use of a piece of pipe over the handle of the wrench. Removal and re-fitting was more problematic.