Vintage BMW Motorcycle Owners

(I have already posted an inquiry on this subject on the /2 facebook group). Group members have been extremely helpful, but this is an 'old school' question.

Here's what I have:
-early R50 bike
-early 1960s generator
-two different armatures, one from original and one from the aforementioned later 6V generator, with magneto and advance

I tried assembling the later armature, but the brushes were only partially contacting the armature, protruding about half-way out. I then installed the 1955 armature, and the brushes were lined up fine. Only thing is, the 80mm Allen bolt offers a great deal of resistance (I chased the threads prior to installing the bolt with an M8 x 1.25 die).

The bolt seems to stop, sticking out about 1". I don't dare tighten any further!

Suggestions?

Regards,

Ken Cruise

Ken
Salis site shows the proper generator bolt should be 12318002205 m8x60mm not M8x80mm

https://www.bmwclassicmotorcycles.com/p ... generator/

m8x70 and m8x80 generator bolt was used on the s models
m8x70 60 watt generator with vibration damper
M8x80 100 watt generator with vibration damper

https://www.bmwclassicmotorcycles.com/p ... on-damper/

Also:
M8x80 allen bolt with a different part # was used on the ignition advance unit

https://bmwclassicmotorcycles.com/index ... m8x80.html

Brushes not lining up
1955 generator should have a 17mm taper
Does other generator have a 20mm taper for the /2 models ?

Tommy

Hi Ken, I read that you used a die before inserting the bolt. A die creates metal shavings (even if they are small or very small), are you sure there are no metal shavings left inside that don't create something that looks like a "plug"? Try to take a look inside.

Marco

Ken

You were given the answer on FB. You have an early R50. It has a 17mm taper on the camshaft. You are trying to put a 20mm generator rotor in it. It can't be done. You need to use a 17mm generator.

Thanks Dave in MI!

I had not looked again, so missed your reply.

I have the original rotor and original armature (I swapped from the newer one with 20mm taper). The brushes are lined up fine.

Re. the magneto-- I tried inserting various sizes of Allen bolt in the magneto, starting with 55 mm, and ending with 64mm. Results are the same -- turns freely with no 'grab' once fully inserted. I looked up this (80mm) Allen bolt (part # 12 31 8 004 100), which according to Salis is used in R50, R50/2, R60/2 and R69, R69S models. I requested this from my local shop.

One commentator mentioned swarf or debris after using a die. I took care to thoroughly clean the bolt before inserting into the magneto opening.

If you happen to see this post please comment on whether I am on the right track!

Regards,

Ken Cruise

A little late in coming, but I got it sorted. The 80mm Allen bolt was correct (listed on Salis for all R50 - R69S models). It is in and properly torqued.

I would have noted this sooner but was away several times this year. Thanks Tommy and others for your replies!

Regards,

Ken Cruise