camekanix Posted March 9, 2009 Share Posted March 9, 2009 Hi all, I have a 76 R-90/6 that needs heads. They were badley damaged by the club fisted mutant who was replacing the valve guides. I have heard that heads from other models from R-75 on up will bolt right up but I am skeptical. Anyone out there have any experience with this? Thanks in advance for any input Link to comment
Huzband Posted March 12, 2009 Share Posted March 12, 2009 It wouldn't make sense for an R75 head to work on an R90, as the bores are different. And so are the part numbers. Check with Beemer Boneyard, maybe they can help with replacements. Linky Link to comment
RPG Posted March 17, 2009 Share Posted March 17, 2009 valve sizes might be different as well. If I'm not mistaken the intake valve diameter is 2mm larger on a R90 than a R75. And as mentioned, the bores are different. rpg Link to comment
DonW Posted March 27, 2009 Share Posted March 27, 2009 The original castings MIGHT be the same, but the factory machine work to create the compression dome, etc. will be different. Used to own a R90/6 (great bike!) and it is a bit unique for engine parts. You can probably swap up to 1000cc jugs, slugs, and heads, and forever have tons of used parts available. Good luck! Don Link to comment
Huzband Posted March 30, 2009 Share Posted March 30, 2009 R100 jugs will NOT bolt up to /6 cases. The spacing of the cylinder studs is different from the /6 to /7. Link to comment
DonW Posted April 1, 2009 Share Posted April 1, 2009 OH! Good to know. All my serious engine work was on post-1981 bikes, which are almost all interchangable pieces. R80ST one day, R100ST the next, and so on. Don Link to comment
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