BMW R51/2 trasmission

[jwonder]

Don't the prewar plungers... and the R51/2... have snap rings? Just looked at the parts book for the prewar bikes, and they definitely have snap rings. I think the R51/2 is the same thing. The "/3" bikes have staked crosses.

My R 51/2 did have a staked cross and I am quite certain it was original. Might be a date specific thing as well as they were changing many items then and things were fluid.

[Goro F]

hello
thx for replies and reccomendations

i had a look at the documentation you suggest me.

here the comparison of what I understood so far: it seems that the pre-war have the snap ring while after war have the cross staked (it is visible from the drawings)

Therefore, considering the same shaft it justified the different dimensions of U Joints. The staked one is more long than the one with snap.

Mosè

[Goro F]

I also just noticed you have snap rings on yours. I have never seen that on an original driveshaft. Anyone correct me if I am wrong, but mine are all staked. Yours have been upgraded. Not bad, just not the original ones. I would question if the length is incorrect and might be putting undue pressure on the hardy disc.

The Barrington manual and likely the shop manual on our site have the correct spacing for the driveshaft.

Thanks, I will go trough your reccomendation!
couple of question:
1- which lenght do you refer that could put under pressure the hardly disk?
2- the spacing you talk is the one showed in the screenshot i attached?

I also share a picture of my driveshaft

Mosè

[jwonder]

It was hard to see your images. I am on an iPhone. You need to mount the final drive in the Motul and measure the distance between the two flanges. The proper distance is in the Barrington manual for plungers.

You also need to know the thickness of the hardy disc you purchase. There are several thicknesses but I think the standard is 26mm.

[Goro F]

hello
the standard dimensions for hardly disk seems to be 26mm

i bought a new one but i did not noticed that the hard rubber of the old one was 31 mm. Now i m in the condition that there is too much clearance between the 2 flanges and the hardly disk.

Maybe also with the old one the assembly was not good, since I measured the leght of the noses and they are 29 mm and with 31 hard rubber thickness cannot completenly pass trough the hardly disk as maybe should be.

Am I wrong? there is anybody that can tell me the right distance between the two flanges or the clearance which shall be between the hardly disk and the flanges? may be round about 27/28 mm distance for a clearance of 1/2 mm?


thanks for help
Mosè