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1989 KDX Front forks not rebounding? Need some help

Posted: 11:15 pm May 28 2016
by dirtbagrider
So recently I replaced the seals on my 89' forks, I filled them with 10wt oil to the 140mm mark, reassembled them and when I was pushing down to make sure they would compress and rebound properly I found that they would not rebound at all but would have to be pulled back to get to the fully extended position. Has anyone had this problem before? Or have any pointers? Thanks!

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 11:56 pm May 28 2016
by KDXGarage
Wow. Perhaps incorrect reassembly?

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 12:09 am May 29 2016
by dirtbagrider
I checked the front fork schematic and if I remember correctly I assembled it right.

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 12:51 am May 29 2016
by KDXGarage
What happens when you pull up the forks?

1989 KDX Front forks not rebounding? Need some help

Posted: 12:58 am May 29 2016
by dirtbagrider
So I looked at the forks again and they rebound alright when not clamped into the triple clamps, but when I clamp them in they don't rebound at all.

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 01:00 am May 29 2016
by KDXGarage
torque wrench??

as in, any chance you are over tightening the clamps?

Clamps out of alignment??

1989 KDX Front forks not rebounding? Need some help

Posted: 01:05 am May 29 2016
by dirtbagrider
I'm not sure what you mean exactly?

1989 KDX Front forks not rebounding? Need some help

Posted: 01:07 am May 29 2016
by dirtbagrider
Ok how tight do they have to be? I'm not very mechanically inclined so any suggestions would be awesome

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 02:25 am May 29 2016
by KDXGarage
Do you own a torque wrench?

1989 KDX Front forks not rebounding? Need some help

Posted: 06:54 am May 29 2016
by ohgood
dirtbagrider wrote:Ok how tight do they have to be? I'm not very mechanically inclined so any suggestions would be awesome
he's hinting that you're putting the fork tubes in a bind by over tightening the triple clamp bolts.

there is a spec for every bolt and nut that is used on the bike. check out the manual, and see what that is.

there will be a vast improvement in the longevity of your fasteners and threaded holes by observing those torques.

1989 KDX Front forks not rebounding? Need some help

Posted: 09:46 am May 29 2016
by dirtbagrider
Yes I have a torque wrench. So I should find out the torque setting for each bolt and set the wrench to that torque? Thanks for all the help!

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 10:14 am May 29 2016
by Julien D
Yes, that is correct.

1989 KDX Front forks not rebounding? Need some help

Posted: 11:05 am May 29 2016
by dirtbagrider
Ok so the situation now is that when I push down on the forks from fully extended position they go in about 1 or 2 inches then they hit the point where they rebound. I think the 2" inches that the fork just slides in is because the inner fork tube isn't having any contact with the spring until it hits that 2" point. Is this ok? Or is there a simple remedy for this situation? Thanks for all the help by the way!!

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 12:16 pm May 29 2016
by KDXGarage
Have you read any on fork spring preload?

Are you certain the fork spring spacers are making contact inside the forks?

1989 KDX Front forks not rebounding? Need some help

Posted: 12:44 pm May 29 2016
by dirtbagrider
For the first 2" of press the spacer is not making contact

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 01:11 pm May 29 2016
by KDXGarage
SWEET. We're getting somewhere. :partyman:

The spacers not only need to make contact, but need to compress the springs a little, as they set assembled. Race Tech recommends about 4 mm of preload (or compression).

In stock form, there are metal tubes inside the forks that provide the preload. You sound like you need to get some PVC pipe and make some new spacers that when assembled, will press the springs down 4 mm.

The length will be correct when you go to install the fork caps.... the fork caps will not screw down all the way without touching the spacer tops. They will touch the top of the spacers 4 mm before being fully threaded down. This will have the bottom of the fork caps touching the top of the spacers (and washer/s), which will then compress the fork springs 4 mm.

I hope that makes sense to you. It took me a while to figure out what it all meant when I got started working on suspension. :blink: :shock: :hmm:

1989 KDX Front forks not rebounding? Need some help

Posted: 01:21 pm May 29 2016
by dirtbagrider
Ok awesome im getting some spacers right now and about it install them! Thank you for all the work! Thats awesome!

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 01:50 pm May 29 2016
by KDXGarage
You're welcome.

You can get some white PVC pipe and cut them to length. I think it is about 1.25" or so pipe. Try to have the ends sanded smooth, so no burrs chip off and float into the oil and compression adjuster assembly.

1989 KDX Front forks not rebounding? Need some help

Posted: 07:08 pm May 29 2016
by dirtbagrider
Ok so I finished the spacers reassembled the forks and put them on my bike took the bike for a quick spin in the rain and the forks work perfectly now! Thank you for all the help and suggestions!!

Re: 1989 KDX Front forks not rebounding? Need some help

Posted: 09:37 pm May 29 2016
by KDXGarage
BOOM!!

We got it done!

Good job.

I love this forum. :partyman: :supz: