Need help finding the reassembly specs for my R51/3 crank

[Grant R26]

I am part way through a total rebuild of my R51/3 and find that there is just a touch of play in the big ends on the con-rods. So this must be sorted to complete the rebuild; (bearings, seals etc etc)

We can ship the crank to Europe or the USA but I have a very experienced local machinist who has done hundreds of crank rebuilds over the decades: all Brit and Japanese bikes...but never a BMW

We have the steel plates made up to press out the pins but don't want to proceed until we have what the machinist calls the "reassembly specs".

We can measure it up and replicate what was but would prefer to work with the factory specs which should be published somewhere

Does anybody out there know where we can find this information please ?

Grant
Toronto

[Beemer100]

Hi Grant,

there is a great book out there written by Hans-Joachim Mai called "1000 Tricks for fast BMWs". In Germany that is the Bible for pre70 BMWs. Now ... the problem is ... its written in German. Don't really know if it ever was translated into English.

Since I don't know what measurements you need exactly, I copied a pic from the book which might be helpful. The 3rd pic from the top describes the endplay which should be no more than 0,03mm. The last pic describes the play at the rods and it should be max 0,07 to 0,10mm.

Another option is Yves at Montercristo in Elgin in case you don't want to go out of country and you wouldn't consider Quebec being out of country ). He is a veeeeery knowledgeable man with regards to pre 70 beemers. Plus he has the machine park to fix close to everything on a bike.

hope that helps
Klaus

[schrader7032]

Would Barrington's latest book on the plunger series have the info on the crank?

[Micha]

I think that what you are looking for is here:
http://salispartsusa.com/parts/wp-conte ... -tools.pdf

[Grant R26]

No Kurt
it is pretty comprehensive but does not go quite that deep.

problem solved...all the detail is in the old 1950 shop manual

thanks again
Grant

[Grant R26]

Well done Michael.
that original BMW shop manual has all the data we need...I have a copy but had forgotten about it as I depend heavily on the Barrington book so much

thanks for pointing that out.

now...on to the crank. Should be exiting

Grant

[808Airhead]

If not you can send it to benchmarkworks,they have a good rebuilder.