The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: scottyintex on March 13, 2011, 11:42:03 AM
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On the 1980 R65 they detuning (leaned) carburetion changes for emissions. The end result was a 5 hp drop from 50 to 45hp. In 1981 the hp was jumped back to 50. If I replaced my 1980 carburetors with 1979 or 1981 carburetors .....would that give me the extra 5 horse power??? I saw a set on sale on ebay and was just wondering.
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Taking a look at the Bing manual and the differences in the 32 mm carbs seems to be main jet, needle, and needle jet sizes .
The '81 model year bikes for the North American market, seem to be set up the 'richest' .
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I replaced my 1980 carburetors with 1979 or 1981 carburetors .....would that give me the extra 5 horse power??? I saw a set on sale on ebay and was just wondering.
I don't think you would see any difference. The R65 was 45 hp all the way from 78 -80 and only went up to 50 hp when 2mm larger valves were fitted for the 81 model so I think you might need the later heads to get that extra 5 hp. Maybe there were also other differences like the camshaft lift or timing. Seems possible as the 50 hp engine makes both it's power and torque at higher revs although that could be because of another obvious difference. The tuned intake system which may well explain some of the jetting changes. Certainly on the R45 engine there are significant changes to the main jet size when the tuned air intake was fitted in 81 although for that engine valve size stayed the same and power stayed the same at 35 HP.