The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: MHSILVERW on February 26, 2015, 01:25:24 AM
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Hi
A query regarding Pre-1981 vs. post-1981 - R45 principally although related to R65 and I guess it's model changes around that time.
I am in the process of acquiring what a 1982 R45 (so the 470cc version of the "smaller twins") which I believe isn't the 'lower powered 27hp German market only version'.
I was reading some posts on here and came across one that was about '1980 vs. 1081 R100RT and there was a comment....
"....That's the thing with these model years, the earlier bike will be more powerful, in theory, but the later bike will be much lighter, so I actually doubt there will be too much in it speed wise...."
I have seen road test(s) of the R45 but they were usually the earlier version and whilst it generally was praised for being smooth and well made, it wasn't deemed a rocket ship.
Tests then (and now?) seemed to think out and out performance was the goal everyone was after and perhaps 'comfort', 'quality', 'sensible', 'proven design' and a 'sound simple design' might not have been that high on the test(ers) or expected readerships radar. Albeit the R45 was/is more powerful (slightly) than the earlier /2 R50 and later R50/5.
Memory tells be that back in the day - the R45 often appealed to the (maybe) more mature rider whose 'racing' / 'tearing' about days were past and it was these other attributes that appealed. I suspect that whilst the R45 would have been 'last/left behind' on the test track (although maybe not as totally eclipsed as might be thought), its handling/sure footedness and 'gait' maybe more suited and less at a disadvantage on the 'street' - in the real world.
I have never seen a test or report on the post 81 version and wondered how it compared and if differed from the earlier version.
I recall reading tests of the post '81 R65 and it was stated as being more powerful with a lighter flywheel, maybe clutch lighter and the Brembo rather than ATE calipers and visually appears to have a different seat (and rear seat cowling) that maybe slightly lower.
I assume the post 81 R45 had the same cycle parts and seat, from photo's I have seen, and I assume the same single cam chain and most likely lighter flywheel although not sure if compression ration/valves were altered. I can see the carbs changed from 'flat top' versions to 'dome top versions'.
But not being a 'overly popular' model I don't recall seeing a road test or report on these 'later' R45's. Does / has anyone experience of these (in relation to the earlier model) and how they are?
I gather some owners found altering the carb needle jet and needle position had a positive effect on "performance" (Mike Fishwick BMW Club UK) saying that mid range and fuel economy were both improved on the post81 version with such 'tweeking', but also some owners said that such 'adjustment' on the earlier models didn't garner any improvements.
Regards
Mark
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One way to tell the difference between a 27 HP and a 35 HP R45 is to look at final drive ratio they will be 34/8 for the 27 and 35/9 for the 35. Even easier look at the speedo ration printed on the lower part of the dial and you will see 1574 on the 27 and 1441 on the 35. If it happens to be a Km speedo they will be 978 or 895.
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R45s were produced from 1978 to 1985 -same as the R65 and R65LS models. The R45 was produced as an attempt to attract buyers limited by some Euro laws as to a smaller displacement engine requirement while riding with a "learner" license, hence the R45 engine's displacement being but two-thirds of the R65.
Both the R45 and the R65 were both listed by BMW as weighting 451 LBS, wet, with 5.8 gallons in the tank.
The R65 was spec'ed by BMW Mottorad at a 108 mph top speed. With both bikes weighting 451 pounds, the R45 topped out, depending on the final drive ratio, at 90 mph with the 8/34 and 100 mph with the 9/35 gears, per the manufacturer.
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the R45 topped out, depending on the final drive ratio, at 90 mph with the 8/34 and 100 mph with the 9/35 gears, per the manufacturer.
I have nothing but admiration for the patience of someone coaxing 90mph from an R45.
Rolley Free anyone?
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The original riders handbook does indeed say with rider prone 90 mph for the 27 Hp and 99 MPH for the 35 HP. Sat upright the speeds drop tp 82 amd 90 respectively.
If it wasn't Rollie Free it must have been a very small guy in skin tight leathers.
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Tires pumped up hard as rocks, one litre of fuel, dead flat road, no wind, small rider who just got off the toilet with time on his hands. Done!