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Magneto: tightening the Allen bolt (1955 R50)
- kenrcruise
- Posts: 86
- Joined: Tue Apr 05, 2011 12:00 am
Magneto: tightening the Allen bolt (1955 R50)
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
- wa1nca
- Posts: 1239
- Joined: Thu Sep 27, 2012 5:15 pm
- Location: Ashfield Ma
- Has thanked: 13 times
- Been thanked: 18 times
Re: Magneto: tightening the Allen bolt (1955 R50)
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
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA
Re: Magneto: tightening the Allen bolt (1955 R50)
Marco
R50/2; R60/2; R69S; R12; R71;
Re: Magneto: tightening the Allen bolt (1955 R50)
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.
50 years of BMW in the garage
- kenrcruise
- Posts: 86
- Joined: Tue Apr 05, 2011 12:00 am
Re: Magneto: tightening the Allen bolt (1955 R50)
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
- kenrcruise
- Posts: 86
- Joined: Tue Apr 05, 2011 12:00 am
Re: Magneto: tightening the Allen bolt (1955 R50)
I would have noted this sooner but was away several times this year. Thanks Tommy and others for your replies!
Regards,
Ken Cruise