Author Topic: Crank cases - non-matching numbers  (Read 880 times)

Offline Duncan R

  • Valued Contributor
  • ****
  • Join Date: Sep 2008
  • Posts: 291
  • Karma: 3
Crank cases - non-matching numbers
« on: 17.10. 2011 18:44 »
Hi all,

I have been offered a set of cases at a good price but the numbers don't match, is it critical that the cases are a matched pair?

Many thanks

Duncan
Anglo - Indian A7SS (Actually is a 650)
Kawasaki ZZR 1100
BMW R80GS
BMW R1100GS

Offline MG

  • Resident Legend
  • *****
  • Join Date: Dec 2009
  • Posts: 949
  • Karma: 23
Re: Crank cases - non-matching numbers
« Reply #1 on: 17.10. 2011 19:28 »
AFAIK crankcase halves have been machined together, so it indeed is critical for crank bearing alignment. Otoh, if you find a good machine shop, that will line bore the timing side bush with the cases assembled and in good alignment with the drive side bearing, you will probably get away with it.
But then there is the question of alignment on the camshaft bushes and the cylinder barrel mating surface(s). For the current prices of good, matched sets, I personally wouldn't take chances there.

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Offline dpaddock

  • NC, USA
  • Valued Contributor
  • ****
  • Join Date: Jul 2006
  • Posts: 429
  • Karma: 5
Re: Crank cases - non-matching numbers
« Reply #2 on: 17.10. 2011 20:32 »
What "numbers"?

David
David
'57 Spitfire


Offline Duncan R

  • Valued Contributor
  • ****
  • Join Date: Sep 2008
  • Posts: 291
  • Karma: 3
Re: Crank cases - non-matching numbers
« Reply #3 on: 17.10. 2011 20:45 »
Hi David,

Each case half has a number stamped on it to show they are a pair. As Marcus explained they are machined as a pair for correct alignment.

Duncan
Anglo - Indian A7SS (Actually is a 650)
Kawasaki ZZR 1100
BMW R80GS
BMW R1100GS

Offline MG

  • Resident Legend
  • *****
  • Join Date: Dec 2009
  • Posts: 949
  • Karma: 23
Re: Crank cases - non-matching numbers
« Reply #4 on: 17.10. 2011 22:06 »
The numbers are stamped on the front of each crankcase half, below the recess for the dynamo.
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Offline dpaddock

  • NC, USA
  • Valued Contributor
  • ****
  • Join Date: Jul 2006
  • Posts: 429
  • Karma: 5
Re: Crank cases - non-matching numbers
« Reply #5 on: 20.10. 2011 02:07 »
OK; Thanks.
David
David
'57 Spitfire