R90/6 with R100 Jugs and Pistons?

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Re: R90/6 with R100 Jugs and Pistons?

Post by jjwithers » Mon Apr 02, 2018 7:59 pm

Another question... will the R90 Rockers and push rods work with the R100 top end?
I might as well use the R100 Rockers but are the push rods the same length?
If so, then they shouldn't make a difference... right?
'77 R100S - http://www.joshuawithers.com/r100s
'73 /5 Toaster Cafe bike http://www.joshwithers.com/slash5
'67 Bridgestone 175 Hurricane Scrambler
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'72 BMW 2002
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Kurt in S.A.
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Re: R90/6 with R100 Jugs and Pistons?

Post by Kurt in S.A. » Mon Apr 02, 2018 8:37 pm

The same pushrod, part 11321262907, appears to have been used for the entire run of Airheads.

Kurt in S.A.

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Re: R90/6 with R100 Jugs and Pistons?

Post by Wobbly » Wed Apr 04, 2018 3:40 pm

jjwithers wrote:
Mon Apr 02, 2018 6:48 pm
Has anybody ever ported heads on BMW's for better airflow? I'm just curious... because I learned to do it on a 2-stroke engine and wondering if it's a benefit to airhead heads as well.
The risk: Porting a 4-stroke without a flow bench is too risky. You could end up possibly screwing up the heads. Nothing you learned on a 2-stroke applies.

The gain: Possibly improving your quarter mile time by 0.001 seconds.

The question: Have you got a spare $400 to buy another set of heads ?
After 20 years as a professional bike mechanic and 30 years as an engineer I know just enough to be dangerous !

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Re: R90/6 with R100 Jugs and Pistons?

Post by Beemerboff » Wed Apr 04, 2018 9:10 pm

Get someone who has the runs on the board do it, Like Richie Moore.
He will probably want to do it properly with new valves seats guides and springs, and this will cost, but folks who have has it done have been well pleased with the results.
Just grinding something out for the sake of it is probably going to make things worse, as Wobbly has already stated, and even on the internet I have never read anyone claim they had made things any better that way.
Guy on ADV did some useful work on his salt racer with a flow bench, but he spoke to Richie first and all he was aiming for was peak power at peak revs for the one run on the salt flat flats.

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