Gen 2 Pressurized Fork Oil?

[Zeus36]

This is a 2012 model with 11,100 miles on the odometer. Right fork had oil running down to the wheel when I pulled off the bike cover. Wiped it down and compressed the forks several times. Fluid blew past the seal. Read the service manual for the fork disassembly and seal replacement. Did some research on this forum and decided to try a Seal Mate. I made my own out of a clear plastic bottle. Cleaned the area again, used a plastic pry tool to raise the dust seal and inserted the seal mate. Oil came pouring out of the fork seal. I grabbed more oil absorbent mats and wrapped the area to keep fork oil off the brake and caliper. Ran the home made seal mate around the fork seal and there was still pressure behind the oil to the point it shot at my face and just missed my right eyeball. There was a bit of dirt on the seal mate leading edge. The seal is better but not 100 percent, so I will likely need to change the seal. Seems like the mileage is too low to have worn seals, so I'm guessing the over pressure is forcing the oil past the seal.

All preload, rebound and damping adjustments had been set a minimum or zero for a soft ride/lower height. This suspension does not use compressed air for the forks. Why would the fluid be under pressure? It is due to being under compression from the weight of the bike? Wouldn't the springs be holding the static load?

Since fluid is relatively incompressible, is something creating air pressure inside the fork? I may try the procedure again, but with the front jacked up so there is no force on the front forks.

 

[02GF74]

my initial reaction is too much oil - is it possible a previous owner overfilled it? (worth checking both sides)

 

[VmaXXX]

I used a Seal Saver on my right fork with front suspended on a Pitbull stand. Oil still shot out while I worked the tool around as fast as I possibly could (I'm not so sure that thing isn't quackadoodle garbage).

 

[butch2000]

curious as well ?

 

[MaxMidnight]

Suspension movement will raise the air pressure within the forks and it will act as a spring.

When the forks are assembled they will be fully extended and the air within will be at atmospheric pressure.
Once the weight of the bike is applied the forks will reduce in length reducing the internal volume within the forks which will compress the air.
If pre-load is reduced this will allow the forks to compress further.

Setting preload, rebound and damping adjustments to a minimum or zero will result in the air pressure in the forks changing more rapidly during suspension movement as there is reduced damping in the system.

It may be this that has caused the seal to leak (conjecture).

(Those who have read my responses to suspension questions know what comes next)....you need to set the static sag to get the best out of the front forks. I would also try different compression and rebound settings as well.

If you need to lower the bike then I'm sure others will offer advice on this.

 

[Zeus36]

MaxMidnight answered all my questions with an excellent explanation!

My original post was August 10, 2022. It is now August 01, 2024.

After using the home-made Seal Mate to clean the fork seal two years ago, I have had no issues with my Second Gen forks.