Throttle Cam Problem

[David]

Friends,

I am again stuck and hope that someone (Mark!?) can help...

The throttle cam on the R26 which I bought earlier this year was broken, and the bike came with a new part, purchased by the previous owner from Blue Moon.

When I went to actually put it in several weeks back, it didn't fit in the housing-- the depth of the larger diameter cylinder which is bored in the brass cam disc was far too shallow. Now the old (I believe original) part had a depth of approximately 5 mm, while the newly machined one had a depth of only about 2.5 mm.

Blue Moon advises that the machinist in Germany has come back and is insisting that all throttle cam discs were the same, about 2.5 mm in depth. Can anyone advise as to whether (a) the singles or R26 actually had a slightly different part or (b) I have the wrong housing or someone has modified the original, which I doubt but is a possibility ??

Thanks again to all!!

David

[Allan Atherton]

The answers provided on the other lists indicate that the throttle cam and housing for the singles and twins are different, aside from the number of cables, and cannot be mixed.

[Thorsten Franz]

Hi,
I fitted the housing of a single to my R50/2 and made following observations:
The housings for the singles R26/27 and the twins of the same period are identical (same part numbers). Mind that the newer version has a provision to fit the round indicator switch.
The throttle cam and the housing cover of the twins are designed for two throttle cables and therefore don't interchange with those parts for the singles.

Brgds
Thorsten

[Mark Huggett]

The housings are different between the R26/27 and R50 - R69S.

R26/R27 Throttle housing:
The stepped boss in the middle, or cam axle has a total height of 3mm +
8mm =11mm

R50 - R69S Throttle housing;
The stepped boss in the middle, or cam axle has a total height of 5mm +
7mm =12mm

Naturally the cam discs have the matching stepped holes in them.

Regards,

Mark
Mark Huggett GmbH

[Thorsten Franz]

Hi,
Sorry, my conclusions apparently lead to incorrect information. The second hand housing that I bought came with a cover only suitable for the singles, but without the cam disc. Fortunately the housing fitted together with the cover and the cam disc I had. That might be considered a happy coincidence.

What made me believe that the housing for singles and twins are identical is the fact that my sparepart catalogue (BMW auxiliary catalogue R26/27, 50/50S, 60/69S gives following information:
Section R26/27: Housing:
32712072347 and 32722072250
Section R50, etc.: Housing:
32712072347 and 32722072250
For the risk of making a complete fool of myself: Does this mean that to identify a BMW part,one must not only give the number but also the model of the bike?
I am asking this because sometimes I order without clearly identifyng for which bike I need the parts.

Best regards
Thorsten

[Mark Huggett]

Hi Thorsten

This subject is complicated, and you can only make a clear full picture if you have a collection of the different editions of BMW parts catalogues from the 1950s through the '60s and finally the last edition of 1972. There you can see how part numbers have changed for these individual parts.

In the last edition (1967) where separate numbers were shown for the Magura throttle assemblies,

R27
Lid 32 72 2 072 263
Housing 32 72 2 072 251

R50 - R69S
Lid 32 72 2 072 382
Housing 32 72 2 072 250

In 1968, the R50 - R69S housing was replaced by 32 72 2 072 347 with the new switch attachment. Due to rationalisation, this throttle grip unit was also then sold for the R26 and R27 as a replacement and that is why you see these two numbers 32712072347 and 32722072250 for all models in the 1972 edition. However, you will also notice that in the 1972 edition, that they have already been replaced with the complete throttle assembly of the /5 series.

Confusing isn't it?. I could write my doctorate on this.

Regards,

Mark
Mark Huggett GmbH