KDXRIDER.NET

I'm rebuilding some 1991 conventional forks. New seals, bushings, fluid etc.

The springs are likely factory spring rate, but I don't know. The bike wasn't rideable when I got it. I have a set of springs for my weight from my old H-series KDX. They are the same diameter, but 20mm shorter than the springs that I pulled out of the 91.

I've never worked on forks this old. They don't have a compression rod running up through the spring and pre-load spacer, threading into the fork cap. On the E-Series, you put in the spring/cap and put in a preload spacer, and simply screw on the cap.

Questions:
1. My manual specifies 618ml +/-4. Is there a preferred fill height method? If so, would you do this with the fork tube extended or compressed?

2. I know I can use the H-Spring, but should I? Should I just increase the spacer length by 20mm or run it as is? I remember cutting down my h-series preload spacerquite a bit, but I suspect these forks don't work the same way.

3. Do I need to bleed out air from the bottom of the fork? My Cyclepedia manual leaves out a lot of details on this subject... for that matter, is misses a lot of details on the subject of forks.

Thanks in advance!

TheGriz wrote:I'm rebuilding some 1991 conventional forks. New seals, bushings, fluid etc.

The springs are likely factory spring rate, but I don't know. The bike wasn't rideable when I got it. I have a set of springs for my weight from my old H-series KDX. They are the same diameter, but 20mm shorter than the springs that I pulled out of the 91.

I've never worked on forks this old. They don't have a compression rod running up through the spring and pre-load spacer, threading into the fork cap. On the E-Series, you put in the spring/cap and put in a preload spacer, and simply screw on the cap.

Questions:
1. My manual specifies 618ml +/-4. Is there a preferred fill height method? If so, would you do this with the fork tube extended or compressed?

2. I know I can use the H-Spring, but should I? Should I just increase the spacer length by 20mm or run it as is? I remember cutting down my h-series preload spacerquite a bit, but I suspect these forks don't work the same way.

3. Do I need to bleed out air from the bottom of the fork? My Cyclepedia manual leaves out a lot of details on this subject... for that matter, is misses a lot of details on the subject of forks.

Thanks in advance!

Forks compressed, springs out

It actually is the same principle, go for about 4mm of preload. The H springs are .35 instead of .30, so that is a bit better, though probably not ideal. Cut the spacers or make new ones from PVC pipe.

There is no cartridge to bleed air from, but move the tubes up and down a little to work in the oil.

Thanks.

2 more questions.

1. Any recommendations on oil height/level?

2. It seems that measuring the preload is a bit different. Let me get this straight: When I drop the spring, spacer, and preload tube in, I guess I should slide up the tube and measure how far below/above the preload spacer sits from the top of the tube, right? If they sat even, it would be zero preload. If it sat 10 mm above the tube, screwing down the cap would give me 10mm of preload... is that right?

TheGriz wrote:Thanks.

2 more questions.

1. Any recommendations on oil height/level?

2. It seems that measuring the preload is a bit different. Let me get this straight: When I drop the spring, spacer, and preload tube in, I guess I should slide up the tube and measure how far below/above the preload spacer sits from the top of the tube, right? If they sat even, it would be zero preload. If it sat 10 mm above the tube, screwing down the cap would give me 10mm of preload... is that right?

Go with stock, then add more if needed.

With the fork fully extended, install spring, washers, spacer tube and set cap on top. The distance from the top of the tube to the bottom of the cap where it screws down into the cap and rests, is the amount of preload. Use PVC and set to your liking.

(the underside of the cap that contacts the top of the tube when fully screwed in)

Awesome. Thanks

You're welcome.