Fork Seal Replacement... Tips?

[Bob_Roller]

You need a pair of snap ring pliers, or you might be able to get the snap ring out with a pair of needle nose pliers, if the ends of the pliers will fit into the holes of the snap ring .

[azcycle]

I hadn't planned on taking anything else apart. Just changed the seals and am going to button everything up. I never ordered new bumpers anyway and it needs to get back together asap as it will be my only form of transportation this week.

Thanks for the help, everyone.

[azcycle]

Got everything back together and took her for a spin... feels great!  I switched the fork legs back to their correct sides so the brake calipers are back behind the legs instead of in front the way they were. Of course, I didn't want to bleed the system again, so I just flipped the calipers so the brake lines make an "X" above the fender.

The front brakes do feel a bit soft and I'm not sure why... I never opened the system up but it feels like a bubble in the lines.  I'm thinking that when the handlebars rotated upside down (to get to the fork caps) maybe I got a bit of an air bubble from the reservoir.  But my next project is to get some stainless lines on teh front and bleed the whole system.

THe most curious thing about the fork rebuild is that either my FIL or the 1st owner put home-made spacers at the TOP of the springs, just under the top cap.  Made out of PVC pipe, about 1.5" in length.  Weird.  But I left them out this time.

[Bob_Roller]

If non-OEM springs were installed, commonly called 'progressive', those PVC spacers are required, due to the replacement springs are a bit shorter than the OEM parts .

I'll bet the top caps on the fork tubes went on a lot easier than they were to take out, with those spacers not installed .

[montmil]

Graeme says, "The smaller one slides down inside the "T" shaped piece but I"m not sure if that is where it goes."

That small metal spacer is not a component of the 1981 R65 fork assembly. I've had both my '81 and the 1983 R65 stripped buck nekkid and that's not a part of the fork leg assembly. PO done his own mod before you got the bike. Check for a similar bit of metal in the other leg. Chunk 'em both in the can.

Here's the exploded view of your 1981 forks.

http://www.realoem.com/bmw/showparts.do?model=0364&mospid=47851&btnr=31_0297&hg=31&fg=10

Monte

[azcycle]

Graeme says, "The smaller one slides down inside the "T" shaped piece but I"m not sure if that is where it goes."

That small metal spacer is not a component of the 1981 R65 fork assembly. I've had both my '81 and the 1983 R65 stripped buck nekkid and that's not a part of the fork leg assembly. PO done his own mod before you got the bike. Check for a similar bit of metal in the other leg. Chunk 'em both in the can.

Monte

Boy, you ain't kidding!  I have bruises on my shoulders from trying to muscle the caps off! To put them on, sans PVC spacers, took about 5 minutes and no where near the muscle.

I don't think the springs are progressive. You can see them in the photo I added earlier in the thread.  Rode the bike into work this morning  and while I can tell a difference with the pvc removed, it's not a BAD feeling... just different. I kept the spacers "just in case" but progressive springs have been added to my wanted list for the future.

I decided the same thing about the spacer.  I had the forks apart to the same degree and since there wasn't a second spacer, it didn't go back. I'm thinking maybe it was a spacer that my FIL used for the non-r65 front fender... but that went back on okay without it, too.

[Barry]

I don't think the springs are progressive.

The original springs are not truely progressively wound but they are dual rate.

Dual rate springs have a number of coils closely spaced which will close up and become rigid thus reducing the number of active coils in the spring. Less coils means a stiffer spring or higher spring rate.  

The original BMW fork springs are  dual rate with 66 coils of which 14 (7 each end) are closely spaced. During the initial travel of the forks the spring has 66 active coils and a spring rate of 26.87 lb/in.  When the 14 closely spaced coils close up there are  55 active coils which gives a spring rate of 34.1 lb/in.

In theory dual rate springs have 2 distinct rates assuming all the closely spaced coils close up at the same time. In reality can anyone notice the change ?

Progressively wound springs have coil spacing which varies "progressively" which should result in a smooth transition  from the lower to the high spring rate.


Just out of curiosity with those spacers fitted you must have had a lot of preload which would tend to make the forks top out easily maybe with a clunk which is what that upper bumper bush is for. Did they do that and if they did have you now noticed an improvement ?

[azcycle]

Barry, the forks DID top out a LOT with a nasty clunk... even just accelerating away from a red light. It was annoying.  To see if there was any difference, I did a quick launch from a stop light this morning (what used to cause most of the clunks before) and it was completely silent up front... no clunks at all.

[Barry]

... no clunks at all.

Good to hear.