Vintage BMW Motorcycle Owners

Hello,

I am restoring an R24 gearbox that has a big crack from an old crash. I am trying to tig weld it but i have a lot of porosity and some heat cracks. I will send it to a proffessional welder as i think that it is over my abilities.
My question is this. If the gearbox casing is not repairable can i use the casing from an R25? are they different?

Thanks in advance!

Most likely not
Salis site doesnt list a part # for the r24
Lists different part # for r25,r25/2,r25/3

https://www.bmwclassicmotorcycles.com/p ... housing-2/

tommy

you can find a parts manual for r24,r25,r25/2,r25/3,r26 if you go into knowledge base select library and type in 25/3
file:///C:/Users/wa1nc/AppData/Local/Temp/PartsManual_R24_1956_German_Rigid_R25R25-2R25-3R26-2.pdf

All have a different part # for transmission cases
tommy

Thanks for the information. So it seems i am stuck with this specific case. I hope a professional welder can fix it.

Alkis the case is the same with R25 1950 model..
i can help you with it...
Andreas

But they have different serial numbers and also some differences in the bearings as i remember. I know that you can use a complete R25 gearbox on a R24 motor but is it possible to use just the casing with the shafts of the r 24?

I have had some good results with some talented aluminum welders. They can groove the crack fill with material and grind smooth. Just have to regain the original casting finish.

I will say this. The aluminum alloy that the cases are made of, is NOT pure aluminum. It is an alloy of aluminum and magnesium. Pure aluminum heliarc rods won't work. Eutectic (brand) welding rods are available that are the correct alloy and will weld BMW cases perfectly without pits, bubbles and imperfections. The case must also be heated up prior to the welding, and be welded while it is hot. Look up suppliers of aluminum magnesium welding rods on the web, give them a call.

I forgot to mention, a wonderful trick:
Years ago, I knew a guy who was the most talented welder I ever knew. This is what he did, (welding the crack in my R17 crankcase, using aluminum magnesium alloy rod) that once the cracked case is welded, and the weld is dressed down to the case surface, the way he make it "disappear" was to take various grades of sandpaper, and not sand the finished smoothed out weld, but to lay the fresh sandpaper over the weld, and tap it with a hammer repeatedly, changing grades of sandpaper. This will imprint the weld with a granular appearance (like the cast surface), and then after the empty case is glass bead blasted, you will not be able to see where the weld is, on the external surface. I know first hand that it works! The repaired crack in the R17 crankcase is almost imperceptible. You have to know where the crack was, and stare at it to find the spot.

Hello Vech,

Do you remember the part number of the Eutectic (brand) welding rods?

Lee