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Bore diameter ?

Posted: Mon May 04, 2015 5:33 am
by Sibbo
I just measured the bore of my ST at 84.8mm is this standard or oversize ? I have to order rings, preferably the right ones .

Re: Bore diameter ?

Posted: Mon May 04, 2015 6:35 am
by ME 109
Don't you have nikasil cylinders Sibbo?

If so, one size fits all. There is no oversize.

Re: Bore diameter ?

Posted: Mon May 04, 2015 7:05 am
by Sibbo
Oopps ! You're right I was looking at this . :oops:
50391
Part No.50391
BMW Part No.
11 25 1 335 218
PISTON RING SET,800cc R80/7 (+0.25mm) 1ST O/S
(PER PISTON)

Re: Bore diameter ?

Posted: Mon May 04, 2015 7:27 am
by ME 109
Sibbo wrote:Oopps ! You're right I was looking at this . :oops:
50391
Part No.50391
BMW Part No.
11 25 1 335 218
PISTON RING SET,800cc R80/7 (+0.25mm) 1ST O/S
(PER PISTON)
That's for the old bikes, not ours. :mrgreen:

How's the original cross hatching in your cylinders?

Re: Bore diameter ?

Posted: Mon May 04, 2015 8:00 am
by Sibbo
It looks pretty good but the rings are shot, a bit of carbon on the pistons but nothing dramatic, just tired .

New needle and jets too.

Re: Bore diameter ?

Posted: Mon May 04, 2015 11:49 am
by Major Softie
Wow, compression, oil scraping, AND correct mixture? It's gonna be a whole new bike!

Re: Bore diameter ?

Posted: Mon May 04, 2015 5:50 pm
by Sibbo
30% more horse power would be good !