BMW R90/6 throwout bearing

Lots of new BMW parts!

Getting this very stiff rubber piece on the piston is tough!   I had to resort to using a small jewelers screwdriver for leverage to pry it on there and it still took about 15 or 20 minutes to get it on straight in the underlying groove.   Just keep at it you’ll get it eventually.

Here is what that blasted needle bearing looks like and the reason for all of this mess.   This is a bad design, BMW dropped the ball here.  The outside edge of these rollers will always try to spin at a faster rate than the inside edge causing these things to partially slide and slip along and eventually wearing out and turning to dust as I found out.

Previous versions of this clutch actuator design instead used a roller bearing with round balls, much better way to go in my opinion.  I have been thinking of a way to use the old bearing in my clutch, I think it can be done by just machining down the face of the piston and a bit of the end that contacts the adjustment screw to compensate for the thicker roller bearing.   More info on the differences and changes of the design over the years on this excellent website here.

With all the new parts assembled in my hands I now understand how this mechanism works, from the drawings I couldn’t quite understand what kept the end of the rod from drilling through the pressure plate (like mine did) without needing to be lubricated.   Now I see, when under pressure to open the clutch the whole rod spins freely (from the silvery bearing forward) and the piston remains stationary.

Like I mentioned before the washer on the end of the pushrod was fused to the shaft on one side and the other end mushroomed and flared out which made the removal of the old rod impossible from either direction.   I had to cut it apart to get it out.  Cue picture of sparks flying because it looks cool.

Continue reading BMW R90/6 throwout bearing

Fall Ride

We went for a nice ride today to get a picture for a scavenger hunt from the CC&D forum which ended up taking us into new territory that I didn’t know existed.  The fall colors of all the cotton woods and aspens were spectacular, quite a surprise.  The colors visible from Santa Fe up on the ski hill had already faded, they usually peak the week of Columbus day and we’d had an early snow which knocked all the leaves off.

We went from Glorieta to Pecos along the old Route 66 winding through the amazing colors and from there we came to a crossroads where I had no idea where we were or where any of the roads went.  We decided to head north and see where the road took us where we found a cool monastery and down a dirt road a lake surrounded by orange and yellow.

Continue reading Fall Ride

BMW R90/6 Clutch

Just a quick follow up on putting the clutch back together after checking for damage and getting new parts in.

I am impressed that the OEM parts come in such heavy duty packaging. You don’t see that much anymore.

Siebenrock clutch disks come pre greased with something.  I went ahead and added a touch of Honda Moly 60 paste on top of this just to be safe.

  • If you have gotten the clutch apart as mentioned earlier reinstalling the parts is pretty easy, just reverse the process.   You will need this special clutch alignment tool, I got this one from Jeff Trapp at Northwoods Airheads.  Use the shorter end for pre-1981 bikes and the other end for post ’81 bikes when they changed the clutch design.
  • Simply install the long screws you used in removal to hold the assembly together while using the alignment tool to make sure all of the pieces are lined up properly. If things are out of alignment you won’t be able to get the transmission on later.

Continue reading BMW R90/6 Clutch