The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Boxer_Bolshie on March 23, 2012, 02:14:49 PM

Title: 1985 and up STANCHION OD diameter?
Post by: Boxer_Bolshie on March 23, 2012, 02:14:49 PM

Am wondering if anyone knows what the stanchion OD is of the 1985 R65 and on and why earlier models ('84 and earlier) are not listed as being compatible with the '85 headlight ears?

Thanks!

Title: Re: 1985 and up STANCHION OD diameter?
Post by: Barry on March 23, 2012, 03:40:04 PM

 Nominal size for 85 on stanchions is 38.5mm early bikes were 36 mm. Actual sizes are a .002" to .003" under. (sorry for the mixed units but I can't visualise tolerance dimensions in mm).                                                                                                                                                                                                                                                                                                    

Title: Re: 1985 and up STANCHION OD diameter?
Post by: Boxer_Bolshie on March 23, 2012, 04:23:44 PM

Thanks Barry!
I guess my next question then would be whether or not the '85 tree would fit on the '84?

Title: Re: 1985 and up STANCHION OD diameter?
Post by: Barry on March 23, 2012, 05:54:13 PM

Carl, I honestly don't know. In 85 the R65 frame was dropped in a rationalisation of the model lines. To make a new R65 a modified 650cc engine was installed in the R80 frame and running gear. So it had little in common with earlier R65's except for the engine.

Title: Re: 1985 and up STANCHION OD diameter?
Post by: Boxer_Bolshie on March 23, 2012, 06:57:35 PM

Thanks again Barry.  I knew BMW started installing the 650cc into the same frame as the larger airheads but didn't know the engine was actually modified.  I also know that after '84 everything else is a monoshock but wonder how (if at all) that changed the front end.  Maybe someone else might know...

Title: Re: 1985 and up STANCHION OD diameter?
Post by: nhmaf on March 23, 2012, 09:11:35 PM

The whole front end of the monolevers is different in construction from the twinshock bikes.   The wheels, brake mounting, fork tubes, lowers, instruments, fender/brace, etc. are a bit different - you'd have to essentially wholesale-swap out the entire front.  The monolever frame ride height is taller, I believe, so even if the steering yoke & bearings fit, I suspect that the fork tube assemblies will be different length, affecting rake/trail.  The top fork brace is still flimsier on the monolevers than the twinshock R65, but I believe you can get a nice billet unit from ToasterTan.

The engine is mostly the same, but is retuned by changing the exhaust system, carbs, and possibly the valve size (can't remember) to move the peak torque of the 650 engine down to around 3500 PRM, where it will do the most good.

Title: Re: 1985 and up STANCHION OD diameter?
Post by: Boxer_Bolshie on March 24, 2012, 01:59:43 AM

Thanks nhmaf.  I was getting the feeling this was going to be a dead end.