KTM AER Fork Failure

DR176
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DR176
Hey guys looking to see if anyone has any experience here before figuring out how I need to proceed. My father has a 19 KTM 350SX-F that we purchased 7 months ago from our local dealer. The thing is mint, with 10.4 hours trail ridden by an old guy who by no means rides hard. Anyway, this weekend riding some single track, the forks locked out fully extended and won't move an inch. of course to get it home I strapped it down and even then the forks still didn't move in the slightest. So, I called up the dealer and of course KTM says it's out of warranty and won't cover it. The dealership can open a claim, and hope that KTM covers it but the service manager didn't sound hopeful over the phone.

Does anyone have any experience dealing with claims with KTM or similar issues with the AER? I've read a bunch on the first versions of the fork getting stuck in the mid stroke when one of the seals takes a dump, but I'm having a hard time finding any info on them locking out like I'm talking about here. Obviously we are talking about a dirt bike here, so I totally get that shit happens and warranty's are tough, but to me it's just unacceptable for this to happen on a bike that is hardly ridden (I know that's a cliche thing to say in a situation like this but take my word for it, it's pristine and obvious visually that the bike has been lightly ridden.) I could start tearing into it, but I'm going to bring it to the dealer in hopes that KTM covers it and their labor as it would really make my blood boil to have to spend any money on this thing.
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slipdog
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slipdog 5/27/2020 1:37pm
5/27/2020 1:37pm
Sounds like maybe the lower air cartridge seal let go and dumped all the pressure into the outer chamber. Did you remove the bleeder screw next to the air valve yet?
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DR176
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DR176 5/27/2020 1:51pm
5/27/2020 1:51pm
slipdog wrote:
Sounds like maybe the lower air cartridge seal let go and dumped all the pressure into the outer chamber. Did you remove the bleeder screw next...
Sounds like maybe the lower air cartridge seal let go and dumped all the pressure into the outer chamber. Did you remove the bleeder screw next to the air valve yet?
I did not, I bled the air out of the air valve just as a brief diagnosis and it let a ton of air out but I've also never bled the fork like that previously so I don't really have an accurate reference on what it would sound like when releasing all the pressure when the fork was fully functioning.
slipdog
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slipdog 5/27/2020 1:55pm
5/27/2020 1:55pm
If the lower seal leaked into the outer chamber a shit ton will come out...
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DR176
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DR176 5/27/2020 2:42pm
5/27/2020 2:42pm
slipdog wrote:
If the lower seal leaked into the outer chamber a shit ton will come out...
cool, any idea why its stuck at full extension rather than sagging like most of the other posts I have read on it? Excuse my ignorance a bit on it, I'm fairly educated on spring forks but with the AER system I'm running blind on only basic knowledge

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slipdog
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slipdog 5/27/2020 3:08pm
5/27/2020 3:08pm
slipdog wrote:
If the lower seal leaked into the outer chamber a shit ton will come out...
DR176 wrote:
cool, any idea why its stuck at full extension rather than sagging like most of the other posts I have read on it? Excuse my ignorance...
cool, any idea why its stuck at full extension rather than sagging like most of the other posts I have read on it? Excuse my ignorance a bit on it, I'm fairly educated on spring forks but with the AER system I'm running blind on only basic knowledge
I'm just guessing from your description but if the lower cartridge seal leaks the pressure from the air cartridge(154+psi) escapes into the outer chamber(0psi) and the pressure will equalize. You will lose cartridge pressure while the outer chamber fills up. That 155 inner and 0 outer will equalize to maybe 70psi and 70psi(wild guess for demonstrational purposes). With 70 +/- in the outer the fork will be topped out and next to impossible to compress. Remember the PSF1 air fork? it used no air cartridge and you pressurized the outer chambers for air spring. They ran at 35psi+/- and used a long balance spring to initiate movement just to overcome the 35psi. The AER has no balance spring because they're not designed to have an outer chamber pressure.

When you hear od the forks sticking down it's because the air piston seal leaked. That means the air stays inside the cartridge but moved from the main side of the piston to the balance side and there's no longer enough pressure on the main side to bring the fork back up to full extension.
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DR176
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DR176 5/27/2020 3:21pm
5/27/2020 3:21pm
slipdog wrote:
If the lower seal leaked into the outer chamber a shit ton will come out...
DR176 wrote:
cool, any idea why its stuck at full extension rather than sagging like most of the other posts I have read on it? Excuse my ignorance...
cool, any idea why its stuck at full extension rather than sagging like most of the other posts I have read on it? Excuse my ignorance a bit on it, I'm fairly educated on spring forks but with the AER system I'm running blind on only basic knowledge
slipdog wrote:
I'm just guessing from your description but if the lower cartridge seal leaks the pressure from the air cartridge(154+psi) escapes into the outer chamber(0psi) and the...
I'm just guessing from your description but if the lower cartridge seal leaks the pressure from the air cartridge(154+psi) escapes into the outer chamber(0psi) and the pressure will equalize. You will lose cartridge pressure while the outer chamber fills up. That 155 inner and 0 outer will equalize to maybe 70psi and 70psi(wild guess for demonstrational purposes). With 70 +/- in the outer the fork will be topped out and next to impossible to compress. Remember the PSF1 air fork? it used no air cartridge and you pressurized the outer chambers for air spring. They ran at 35psi+/- and used a long balance spring to initiate movement just to overcome the 35psi. The AER has no balance spring because they're not designed to have an outer chamber pressure.

When you hear od the forks sticking down it's because the air piston seal leaked. That means the air stays inside the cartridge but moved from the main side of the piston to the balance side and there's no longer enough pressure on the main side to bring the fork back up to full extension.
Hell yeah, thanks for taking the time to write that. It makes total sense and If I'm understanding correctly, the next diagnostic step would be to remove the bleeder screw next to the air valve and if that bleeds off the outer cartridge, and the fork collapses, we know it's that lower cartridge seal?
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slipdog
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slipdog 5/27/2020 5:12pm
5/27/2020 5:12pm
DR176 wrote:
Hell yeah, thanks for taking the time to write that. It makes total sense and If I'm understanding correctly, the next diagnostic step would be to...
Hell yeah, thanks for taking the time to write that. It makes total sense and If I'm understanding correctly, the next diagnostic step would be to remove the bleeder screw next to the air valve and if that bleeds off the outer cartridge, and the fork collapses, we know it's that lower cartridge seal?
Yes, that is correct! Especially if you let all the remaining air out of the air chamber
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SEEMEFIRST
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SEEMEFIRST 5/27/2020 5:43pm
5/27/2020 5:43pm
Slippy knows a thing or 3 about suspenders.
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captmoto
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captmoto 5/27/2020 6:46pm
5/27/2020 6:46pm
I think that was an issue with some of the early air forks but I thought that was worked out by WP. Slip Dog knows the fix but you might be able to get it warrantied at your local shop. I had Racetech do my suspension and they replaced that seal with something of their own so it was a known problem in 17. I haven't had any issues but I'm only at 54 hours.
Bruce372
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Bruce372 5/27/2020 7:28pm
5/27/2020 7:28pm
Nothing is perfect, but they are good forks once setup.

The better news , is that fork is really easily worked on, more than any spring fork. That's the beauty, its like the ak47 of forks. Wp makes rebuikd kits with all the appropriate seals etc. Basic suspension tools are fine, wp has a special cart seal tool but you can improvise with a tear off!

Just service the forks and I am sure you will be golden

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