From: matthews@ajsh.colorado.edu (Alex Matthews)
Subject: Fork seals (excruciating detail)
Originator: matthews@ajsh
Organization: JILA, University of Colorado at Boulder
Distribution: na
Date: Mon, 13 Apr 1992 20:20:36 GMT

Thanks again to all who all who calmed my fears about fork seals a while
back.  This past weekend I successfully replaced the fork seals on all
three bikes, with only a few minor aggravations.  It was easier than I
expected, perhaps because through experience I have learned that having
all required tools *plus* a few more that you may not expect to use is
invaluable in getting a job done.  I just happened to guess right about
what extra tools I would need.  Total wrenching time was 1.5 hours for
each GS450, and 4 hours for the befaired GS550ES, which also requires 
brake fluid bleeding when the forks are removed.

The single most valuable tool turned out to be the electric impact
wrench (Chicago Electric, $90 from Harbor Freight tools); the manual
recommends using an impact wrench on the forks, but for me it was 
required.  The Suzuki damper rod holding tool was next to useless.
Also, I had to scrounge around to find adaptors that would allow the
impact tool to reach the recessed hex bolt in the right legs of the 450s;
this design flaw was apparently corrected by the time they built the
550 in 1984.  In short, nothing went as smoothly as the manual predicted,
but I was over-prepared and everything worked out okay.  Total parts cost
was in the neighborhood of $25/bike for seals and dust boots, 
and I saved the approximately $40/bike labor charges that 
I would have paid if I'd brought the forks in to the dealer.  
The savings went beyond the tangible, though.
I am more than ever convinced that the investment in the tools was worth
it.  The seal in Katy's bike that never quite sealed properly turned out
to be poorly installed by the dealer.  Not only that, but the seals
they put in last year did not resemble the seals that have been in use 
in the GS450 since 1985!  I suspect the dealer just put in whatever fit
from the leftover bin.

I had no trouble tapping the new seals in with a rubber mallet, using the 
old seal as a drift punch.  On the 550 I could use the retaining washer 
to tap against.  The fork internals are greasy but very simple, and the
new teflon bushings were a breeze to install in the 550 (the old bushings 
were very worn at 30k miles).  Reassembly was trivial and fast.

The only frightening moment was when I peeled back the dust boots on the
550 and discovered mounds of rust where the retaining washers used to be.
Water had settled in there and made a mess that can only be described
in marine archaeology terms; despite having lost much metal the (probably
unobtainable) washers were still serviceable under all that scale.
The old seals showed no signs of wear or deformation;  I suspect that 
they were just victims of years of dirt and dust packing into the 
area that contacts the tube, as several people suggested.  With
that in mind, I made a trip to the BMW dealer to buy some fork cond...
er, gaiters, to better protect the fork tubes and seals from dirt.
The BMW pieces are excellent black, thick, resilient rubber, and even the
hose clamps have a certain cachet that transcends Japanese and US parts;
I paid $30/pair for the gaiters and $.50 apiece for used clamps.
Compression of the forks is now accompanied by the hiss of air expelled
from the small vent hole. The gaiters give the front of the bike a bit of a 
galumphy off-road look; could this be the first GS550GS?  How symmetric.
-- 
-Alex Matthews (matthews@ajsh.colorado.edu)
DoD #0010   
"Every particle continues in its state of rest or uniform motion in a 
straight line except insofar as it doesn't."  -- Sir Arthur Eddington