I brought this up over on the FB page but as yet, there has been no solution to the problem.
I bought the bike used this summer. It has 25,000 miles on it. As soon as I took it for a test ride, I knew right away something was amiss with the forks having excessive dive when braking. I also have an '81 RS, so I know what the proper feel is for the forks on these bikes.
I started out with new seals, lower inspection, new Progressive springs, and went with 10W oil. Made no difference. Now that it's cold, I put it on the lift and took the forks completely apart. Outside of two extremely small scratches in one of the guide rings, I can't find anything wrong with parts. I have no idea what to do next. Help!
► If the rate of dive is too fast, then try the next higher increment in viscosity (15W) fork oil. (You are using real fork oil aren't you, and not some motor oil, right ?)
► If the distance of dive is too great, then the spring weight needs bolstering. You'll need to remove the fork cap and add a solid tubular piece on top of the spring. Start with a PCV plumbing coupling or cut piece of water pipe, then add flat washers as needed.
Play with those 2 adjustments and you can dial it right in.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Yes, I'm planning to try 15W oil this time. Increase spring preload with longer spacers, even though these items are way out of the normal range. Time will tell.
I have a spare set of those springs and they measure 535mm long. Next time you have the caps off, pull them out to 1) make sure both are the same length (within 2 or 3 mm). Then check the free length to insure the springs haven't collapsed. Adding spacers to a collapsed spring may get you into a coil binding situation leading to zero front suspension movement.
I'm running 15W Bel-Ray synthetic fork oil in my 1979, and generally compress the springs a little over 1 inch on installation.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
My Progressive springs measure a hair over 519mm long. And yours are the Progressive brand? What bike do you have? The stock BMW springs with the plastic ends measure 556mm long.
Regards.
Not exactly. I bought Progressive brand springs to install in my '79 R100 RT. When I pulled the existing springs out, they were progressively wound. I should have returned the new springs, but to be safe I swapped them out not knowing the older spring's history.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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