WP AER Forks Collapsed after Rebuild then Extended Back to Normal

Vonripper450
Profile picture for user Vonripper450
Posts
133
Joined
5/31/2013
Location
Colorado Springs, CO, USA
Vonripper450
My friend rebuilt his AER forks and everything appeared to be good to go until he tied the bike down for a while. The forks eventually collapsed but, after putting the bike on the stand for a while, the forks extended and have 150# pressure on them which is the pressure they started at. He rode around the yard after they re-extended and checked, no pressure lost. Is it possible the seal between the positive and negative chamber leaked a bit then sealed? Would you tear it down or try to run it. Thanks guys for your help! It is much appreciated.
|
Rickyisms 8/14/2022 1:32pm
8/14/2022 1:32pm
I would tear it down. Something about them collapsing on the face of a jump seems pretty terrifying.
MX558
Profile picture for user MX558
Posts
1998
Joined
4/1/2008
Location
USA
MX558 8/14/2022 3:10pm
8/14/2022 3:10pm
That happened to me but not after rebuild . It was the second issue with air forks with KTM . I went KYB conversion and couldn't be happier
Bruce372
Profile picture for user Bruce372
Posts
6329
Joined
4/1/2008
Location
USA
Bruce372 8/14/2022 5:12pm
8/14/2022 5:12pm
If they are functioning correctly after a quick ride, you should be fine. After rebuild of the air piston seal, they can act a little strange from grease filling the air bypass slot. At least, I experienced this.

They are reliable forks, and easy to service but easy to service wrong also, but just make sure it's been done properly and is safe to ride. There are special tools from ktm to rebuild both piston and cartridge seals, but there are work arounds also if you know what you are doing.
2
Broseph
Profile picture for user Broseph
Posts
1234
Joined
4/28/2018
Location
Stevenson, WA, USA
Broseph 8/14/2022 6:49pm
8/14/2022 6:49pm
Vonripper450 wrote:
My friend rebuilt his AER forks and everything appeared to be good to go until he tied the bike down for a while. The forks eventually...
My friend rebuilt his AER forks and everything appeared to be good to go until he tied the bike down for a while. The forks eventually collapsed but, after putting the bike on the stand for a while, the forks extended and have 150# pressure on them which is the pressure they started at. He rode around the yard after they re-extended and checked, no pressure lost. Is it possible the seal between the positive and negative chamber leaked a bit then sealed? Would you tear it down or try to run it. Thanks guys for your help! It is much appreciated.
Sounds like the piston is slowly leaking air. After being tied down for a while, air leaked past and equalized pressure on each side.

Not really a big deal, the forks are made to leak air around the piston and equalize right before they top out. So as long as the leak stays slow, it will be corrected each time the forks extend. Probably won’t even notice it in normal use.
3

The Shop

See All »
Motoxtombo
Profile picture for user Motoxtombo
Posts
1119
Joined
4/1/2008
Location
Holyoke, MA, USA
Motoxtombo 5/10/2024 5:25pm
5/10/2024 5:25pm Edited Date/Time 5/10/2024 5:54pm

I had this happen today, but its a new bike, a 2024 KTM 250SX, with less than 2 hours on it. The forks haven't been apart. I noticed bike bike flopping from side to side in the rear view mirror in the back of my van, it has been tied down for a week in the van, with the plastic fork brace in place. I try not to leave it tied down that long but I didn't have a choice this week.

The tie-downs didn't slip, I got the bike unloaded and on a bike stand and I checked the pressure and it was at 118 psi, I had it set to 155 psi, I went to get a torx driver to loosen the bleed screw to see if anything came out, It took a little while to find the right size and by the time I got back to the bike the air pressure was at 153 psi, I loosened the bleed screws anyways and nothing came out.

I took the bike off the stand and the forks felt fine, I road the bike around the yard and everything felt fine.

 Do you think once the forks break in this won't happen?

Thanks

Post a reply to: WP AER Forks Collapsed after Rebuild then Extended Back to Normal