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R69S poor compression

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Flathead57
Posts: 5
Joined: Tue Apr 10, 2018 10:20 pm

R69S poor compression

Post by Flathead57 »

Hello everyone
I just rebuild R69 engine but modify to R69S and did 1500mile run in.
new R69S piston new camshaft (RS stamped) new lifter new timing gear set
restored R69 crankshaft (SALIS did it perfect )
very easy to start but the spark always serious dark poor idle and very weak at low rpm.and always backfire
I tried the timing light to check at idle.it just on S mark and up down around 1mm.
so i checked the cylinder pressure.only 100 psi after 6-7 hard kick.and intake clearance around 0.06in
than i adjust clearance to 0.11in and check pressure.it go up to 155psi you can feel the kick pedal become
harden
Ride with 0.11 intake clearance no any backfire and more power at low rpm.
try adjust to 0.16in than first kick already 80psi after 3kick already 160psi.
and i try to did the leaking down test it is good.valve without any leaking.
I change another R69S cylinder head on and all the same.
Checked the timing gear line is matched.but it like camshaft timing wrong.
its R69S 320degree camshaft with RS stamp.is that possible camshaft issue?
Wish any one had any experience like this and tell me what's going on?????

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schrader7032
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Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX
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Re: R69S poor compression

Post by schrader7032 »

Welcome to the forum! I'm not sure I fully understand the changes and setup, but intake clearance is 0.15mm or 0.006" and exhaust is 0.2mm or 0.008". Could that be an issue?
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

Flathead57
Posts: 5
Joined: Tue Apr 10, 2018 10:20 pm

Re: R69S poor compression

Post by Flathead57 »

I did few R69S and never like that.some times I will set up intake for 0.1mm and ex for 0.15mm let it little
quiet and ride very hard still have good idle.
But this time i really don't know what's going on.
timing gear line is fine so only maybe the camshaft have issue
or some where i can check?
wish any one have suggestion
thanks

Daves79x
Posts: 680
Joined: Sun Aug 09, 2015 8:13 pm
Location: Knox, PA. USA
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Re: R69S poor compression

Post by Daves79x »

Question for me is why you modified the best engine BMW ever made?

Dave
Dave

Flathead57
Posts: 5
Joined: Tue Apr 10, 2018 10:20 pm

Re: R69S poor compression

Post by Flathead57 »

Hello Dave
Because owner bought this engine from Germany and didn't come with R69 magneto
without it i am not sure what's going on.and i think it so rare and difficult to find a good one.
so owner choice modify it to R69S.but i think it is easy back to R69.
Thanks

Flathead57
Posts: 5
Joined: Tue Apr 10, 2018 10:20 pm

Re: R69S poor compression

Post by Flathead57 »

Or any one fit 344° RACE camshaft and test cylinder pressure ?
Thanks

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