The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: badbmwbrad on August 28, 2019, 07:51:08 AM
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[size=14]My friend's 1982 R65 suffers from engine vibration at highway speed. His other Airhead is a 1983 R80RT which needs some chassis work but whose engine runs great (smooth, tractable power). I suggested that he simply replace the R65 engine/trans and final drive with those on the R80RT.
My research on this forum indicates the R80 engine will fit in the R65 frame as long as the proper hardware was also imported with the bike. I'm not sure what additional hardware is needed except possibly the engine mounting fasteners.
The R65 driveshaft is shorter. Will the R80 transmission and final drive connect to the R65 driveshaft and final drive? [/size]
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Ok, as one who has done this conversion, rather than the armchair warriors that infest the internet (not this group though it must be said) I offer the following.
The R80 engone will bolt straight in to the R65 frame - the main frame of the R65 is identical in dimensions to every other /5/6/7 and monolever/paralever airhead frame.
The 82 R65 and 83 RT have the same ignition system and the same clutch/flywheel so physically the R80 engine is a direct swap for the R65 engine.
The only things that will cause you grief is the intake trunks and the exhaust system. In both cases the answer is simple - use the airbox, intake trunks, headers and exhaust from the RT. You may have a slight overhang in terms of the length of the mufflers, but I suspect you will be the only person who notices.
Lastly, if this is only a short term gig I'd leave the R65 final drive in place - the acceleration available with a healthy r80 engine up front is quite interesting. And it means that your speedo remains accurate.