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Thread: Cylinders and Head swap for an R90/6

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    Cylinders and Head swap for an R90/6

    Does anybody see any potential problem in swapping out the cylinders, pistons and heads of a 1976 R90/6 with these? http://www.ebay.com/itm/BMW-1994-R10...3a9b7f&vxp=mtr They are from a 1994 R100GS R100R airhead motor.

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    Someone will need to check me to be sure, but I believe the Nikasil cylinders have a ridge around the spigot that fits into the case. This will have to be machined off in order for these cylinders to work.
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    '78 R100/7 & '69 R69S & '52 R25/2
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    Quote Originally Posted by banzaibob View Post
    Does anybody see any potential problem in swapping out the cylinders, pistons and heads of a 1976 R90/6 with these? http://www.ebay.com/itm/BMW-1994-R10...3a9b7f&vxp=mtr They are from a 1994 R100GS R100R airhead motor.
    You'll have to do a bit of research as it was year 1976 ( and possible some late 1975's ) when they changed the blocks to accommodate the newer style cylinders. The early years R 90/6 74 & 75 and possibly early 76s ( you'll have to use the manufacture date of your engine to know for sure ) would not accept the newer cylinders. You can modify the block or possible cut a recess in the cylinder to make it fit on an older block if you want to go that route.

    The big change was that the older blocks used an aluminum spacer between the block and the cylinder and the newer ones had an O ring groove cut into the cylinder. Also the block itself was opened up slightly to allow the O ring equipped cylinder to slide into the block.

    I do know that the R90 & R75 cylinders ( not the S model ) are interchangeable for years 74 & 75 up until about Sept/75 when they changed the blocks.
    1971 R50/5 SWB with R75/6 drivetrain
    2013 DL650

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