The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: manxr65 on September 04, 2010, 01:56:38 PM
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i'm wanting to give my r65 a bit better top end speed , so whats the change to do , bevel drive , if so what ratio is better, or will an r80 head fit straight to the 65 engine .
mine is a 1979
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Quickest way, would be to change the final drive .
The engine doesn't take to well to 'improving' it, seems to lead to early demise of the engine .
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ok so the bevel drive is best then , i have a 32/9 on at the moment , whats the best size to got to .
will a r80 or r100 fit straight on
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You need to find a final drive with a lower numerical value than you have now .
Yours is a 3.56 ratio .
I think I saw a final drive ratio of 3.44, I think it's from the R45 series bikes .
Barry made some posts a while back about this, hopefully he'll see this, and set the record straight .
I really don't know if an R80 or R100 final drive will work or not, I believe they have larger wheels, if that makes a difference or not .
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Here's the data for the 37/11 or 3.36 final drive. This is the lowest numerical ratio fitted to an R65 according to reports I collated from owners and probably the lowest you should fit.(http://)
and also your current 32/9 or 3.56 (actually 3.555555) ratio for comparison(http://)
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After all is done and said, if you find a final drive with the 3.36 ratio gears, I think you would only gain about 7% on the top end speed compared to what you have now .
It's been said before about the R65, if you want a faster bike, buy one .
The R65 was intended to be a beginner bike .
If you want a faster airhead bike, get an R100 it will be cheaper and less problems than trying to make your R65 faster .
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"I really don't know if an R80 or R100 final drive will work or not, I believe they have larger wheels, if that makes a difference or not ."
Bob, I think almost all airheads use a 4.00 x 18 rear tire.
105 seems plenty fast for my R65, I'm not souping it up.
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The 1985+ R65 bike engines were retuned for torque peak lower in the RPM band and fitted with the same 3.36 final drives that the torquier R80 engine had, but apparently the R65 engine could pull it without too much difficulty. If you go to a "taller" final drive like a 3.0 or 2.92 from an R100, I think that you'll have to do alot more frequent shifting, and revving the motor alot more to achieve decent acceleration & overtaking, plus being more likely to lug the 248 engine, which really shouldn't be lugged (the Type 247 engine in the R75/R80/R100 bikes shouldn't be lugged either, but they are still tuned for lower torque peaks than the rev-happy 248 engine).
There was a time when I pursued triple digit speeds on public highways on motorcycles - fortunately I think that I'm mostly past that now and am quite happy keeping my motorcycles below the ton (though sometimes not too far below it). Speeding tickets round these parts for doing 100+ MPH will get you put in jail, automatically, anyhow.
One advantage of the 3.36 final drive on your R65 might be to nudge the typical "buzzy" point that usually occurs just above 4500 RPM on my bike to be around 70 MPH - thus you could cruise at the typical speed limit in a smoother RPM band for a few more MPH. I generally just either ride the thing at 62 MPH, or else at 72 MPH, and avoid the buzzy area altogether with my stock 3.56:1.
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+1 on getting a bigger bike.
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+1 on getting a bigger bike.
+2 Im with Rob have a peep at this
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=220665212384&ssPageName=STRK:MEWAX:IT
If you dont buy it i might, there was a R100 in Cumbria went for 750 a few week back all it needed was a push rod seal.
Lou
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I was surprised that the R850 was still in production, it was only imported to the US in '95 and '96 .