R90S Flywheel Ring Gear?

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rd400f
Posts: 17
Joined: Thu Apr 24, 2014 3:20 am

R90S Flywheel Ring Gear?

Post by rd400f »

Hi
Is the ring gear on the flywheel removable?...as in heat shrunk on?

Or are the teeth integral to the whole flywheel?

I have bad teeth and not the ones I brush each morning.:(

Thanks
Richard

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schrader7032
Posts: 7871
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: R90S Flywheel Ring Gear?

Post by schrader7032 »

Yes it is heat shrunk or possibly staked to the outside of the flywheel. Have not heard that people have tried to replace just the ring gear...I suspect the way to go is to buy a new/used flywheel.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

rd400f
Posts: 17
Joined: Thu Apr 24, 2014 3:20 am

Re: R90S Flywheel Ring Gear?

Post by rd400f »

Hi
Do you know which models flywheels are compatible?

Assuming I get the correct starter motor to go with donor flywheel?

Thanks
Richard

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schrader7032
Posts: 7871
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: R90S Flywheel Ring Gear?

Post by schrader7032 »

RealOEM says that part number 11221256966 was used on all /5 and /6 bikes 1969 - 9/1975. There was a different part number for /7-on through 1980. Seems like there were some issues with the size of the bolts/holes into the crankshaft for the early bikes. Not to mention that the timing marks changed during this time period. The first /5 through the '74 R90S had 10mm bolts, then for the '75 models 11mm bolts. With those '75 models, timing was 9 deg BTDC and 34 deg BTDC static and full advance. But then for the '78 emission models, the bolts were 11mm but the timing switched to 6 deg and 32 deg. Because of these variations, best to find your exact year flywheel.

Snowbum discuss flywheel bolt torques near the bottom of this page...this gives more info on when changes were made:

https://bmwmotorcycletech.info/clutch.htm
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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