Camshaft options for R65 ,1978.

[haggis_australis]

Hello out there, I want to renovate my '78 R65(it was a R45 originally).
I would like to do it in a cafe racer style, without too much modification to the engine. However I'd like to know what camshaft options are available, I don't really want full race spec' cams , but a bit more sporty would do. Hope you can help, ta.

[Rob Valdez 79 R65]

[movedhere] R65 Technical FAQ/Procedures [move by] Rob Valdez 79 R65.


I've never heard of an optional camshaft for the R65 engine.
But that doesn't mean they are not out there.

The best way to make a R65 go faster is on the bathroom scale.

[Barry]

This suggests there are no sports cams for the R65

http://moragafalconers.org/BMW_336_cam/Sport%20Cam%20Installation%20Draft.pdf

Bear in mind though that the later 50 BHP R65 already has the highest specific BHP/L of any of the airheads.

R90S beats it on torque though.

I'm curious, does anyone know where the 336 comes from. I have tried to understand it from the cam timings but can't get anything to add up to 336. Might be because the timings given are with zero clearance which is not usual.

[Barry]

A little more information on cams.

If you read snowbums page on cams he refers to that morganfalconers pdf file and makes a comment about the 336 cam " it is questionable that the cams won't fit the R45 and R65" meaning he thinks they might. Still you would be very much on your own to do it. http://bmwmotorcycletech.info/cams.htm

The only other thing I found out for sure is that our stock cam is a 308.

I'm still not sure what 308 and 336 means. The quoted inlet cam duration is 240 deg for the 308 cam and 264 deg for the 336 cam but that's measured from .080" valve lift.  

It's possible that 308 and 336 are cam durations from zero valve lift.  You might think that the crankshaft wouldn't rotate 68 deg in the case of the 308 cam for .080" valve lift but it may well do as the initial clearance ramps are very shallow.

[Semper Gumby]

[movedhere] R65 Technical FAQ/Procedures [move by] Rob Valdez 79 R65.


I've never heard of an optional camshaft for the R65 engine.
But that doesn't mean they are not out there.

The best way to make a R65 go faster is on the bathroom scale.

And lighten the flywheel while your at it.  San Jose BMW Still does it I think...

[Motu]

" it is questionable that the cams won't fit the R45 and R65" meaning he thinks they might.

You just have to see a standard airhead cam and an R65 cam side by side to see why they are not going to work.I wonder how different the R65 mono cam is - the difference in torque curve can't be just because of the lower compression alone.There is a slight hp drop to 48hp,and a larger drop in torque to 34.7 ft/lbs - but the rpm for max torque drops from 6,500rpm to 3,500rpm,giving a much wider powerband.

The 50hp R65 is slightly quicker to 100kph than the R80,and a full second quicker than the R65 mono - but that's more likely due to the R65 mono having the same final drive as the R80RT.

[Rob Valdez 79 R65]

And lighten the flywheel while your at it.  San Jose BMW Still does it I think...

Or just bolt on a starter ring/clutch carrier from a '81-on.
If it is a '81 & later, there isn't much metal to remove.