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Old 07-16-2012, 04:13 AM   #16
chasbmw
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I have taken some rough and ready measurements of the outside of the cylinder of my R90/6 and of the 1070 bike.

R90/6. Is 118.6 mm

1070. Is. 122.4 mm

These are rough and ready measurements just measuring the diameter of the cylinder between the fins.
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R90s 1070 replica, R90/6, 1958 R50
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Old 07-16-2012, 02:06 PM   #17
mattcfish
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Quote:
Originally Posted by chasbmw View Post
Back in the old days if you wanted a larger than stock engine, you had to take a BMW steel lined cylinder and bore it out, im not sure if special liners were fitted, but in any event the liner would be thinner than standard as the operation was constrianed by the size of the existing BMW cylinders, these were often fitted with venolia pistons. These are the setups that according to SS have developed corrugation.
Nowadays we have the luxury of the kits coming out of Germany mainly sold under the brand name Seibenrock which feature new aluminum cylinders faced with nikilsil and no steel liners.
Yeah, the Seibenrock barrels are cast in Italy if I remember correctly.
I thought the pistons were Wossner not Mahle though.
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Old 07-16-2012, 02:26 PM   #18
Airhead Wrangler
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Originally Posted by mattcfish View Post
Yeah, the Seibenrock barrels are cast in Italy
Gilardoni? At some point didn't they cast OEM BMW barrels? Didn't Mahle at some point also?
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Old 07-16-2012, 03:07 PM   #19
chasbmw
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I don't know who makes the pistons for the 1070 kits, the modern lightweight pistons I fitted to my R90/6 were made. Y wossner.
Charles
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R90s 1070 replica, R90/6, 1958 R50
1971 Commando Fastback
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Old 07-16-2012, 04:10 PM   #20
RGregor
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Quote:
Originally Posted by chasbmw View Post
I don't know who makes the pistons for the 1070 kits, the modern lightweight pistons I fitted to my R90/6 were made. Y wossner.
Charles
The first (small) series 1070cc kits came from Gilardoni. They also had other conrods then and a slightly different piston shape.
Now (at least for the last three years) pistons and barrels come from Mahle.
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Old 07-16-2012, 05:09 PM   #21
bernardofeio OP
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hello



what is the weight of the original bmw r100 pistons? "Mahle sport kit standard" have 604g that seems to me a bit heavy. Moorespeed 12,5:1 are 415g

97mm, 10,5:1 compression and some light pistons would be near to perfect!


one more question. these 1043cc kitks need altering the heads of are they prepared to be used without this mod?
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