The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: dmsantam on January 03, 2025, 03:35:43 PM
-
hi all, i have a 1985 r65 mono and the front forks leak from the top. I have the second version of the forks in the diagram attached. From the top, there is plastic fork cap (1), allen head bolt (2) with oring (3) into 36mm nutted fork cap (4), upper fork plate (not pictured), steel washer (5), fork stanchion (6). The leak appears to be coming from the interface between #5 and #6. Is the perfectly machined surfaces of these two items providing the seal? In my experience there has always been an oring on the fork cap (4), but that doesn't seem to be the case on this bike.
The top of the fork stanchion is not perfectly smooth, like somebody has hammered on it before, so that's maybe the issue here. Can I use something like thread sealant with PTFE on the upper few threads of #4? Interested in your thoughts, thanks.
-
Looks like item # 5 is a crush washer .Either it needs to be replaced or the parts need to be tightened .
-
The hammered finish on the sealing surface won't be helping. I'd be inclined to stuff a rag into the top of the stanchion and then try to improve the surface finish by grinding or using wet & dry depending how bad the damage is.
-
I would also clean the face up. Rag and grease down the hole first, pop the fork up a bit if still on the bike, then a large flat file. I'd avoid abrasives unless you are sure to catch all the debris. New washer, or anneal it if its not out of shape.
You can get Loctite (and similar) liquid (pipe) sealants. Stuff designed for large threaded pipes that you can take apart again. Not (fastener) thread sealants, which you might never get apart again in this size thread ::)
-
Don't ever use PTFE tape on a fine thread on a motorcycle as it's not designed for that.
If you are using a Loctite based thread sealant, then use a thin line on two or three threads only. Don't drown the thread in the stuff. That was how a company Rep. explained to us how to use it many, many years ago. Always put the cap back on after use and keep it in the fridge to prolong its life.
-
The steel washer is never going to seal unless the surface is perfect. They must have thought that little or no oil would get this far up.