Is it the fork seal that wears out?

[imortlfool]

Does the fork seal itself wear out, Or does the gunk in the fork collect at the bottom and work itself between the seal and the chrome?

This is why you can clean it out with a business card for a short term fix?

I can't see with my eyeballs the difference between a new seal and a cleaned up 25,000 mile seal. The dust wipers are cracked by the sun. The fork is full of gunk.

Of course by the time you do all the work to clean the inside of the forks, may as well put in new seals.

 

[N4teTheGreat]

Seals loose their elasticity over time and become more prone to leaking. In off road applications dirt can build up under the seal causing them to leak prematurely, so an attempt to clean them is worth the effort, but if they start leaking again after that, it's time for new ones. Seal Saver or something similar can buy you time in a pinch.

 

[bluegixxer600]

Little rock nicks in the stanchions can damage the seals and cause leaks too. This is less common as most bikes these days have little deflectors to help prevent debris damage.

 

[Escape pod]

The gunk at the bottom of the fork tubes comes thereby the dust wipers, especially if it has cracks.

 

[ST Guy]

Mostly it’s wear. But it can also be a defect of some sort on the outside of the tube.

 

[imortlfool]

The forks took three rinses with a cup of diesel to rinse clean. Gunk.

A machining chip was in the grease in the threads of one of the caps. Old seals original.

I did have a nick way down at the bottom of one fork, where it rarely goes, I sanded it with 2000 grit and put a drop of superglue on it and sanded that.

 

[dmfdmf]

Little rock nicks in the stanchions can damage the seals and cause leaks too. This is less common as most bikes these days have little deflectors to help prevent debris damage.

Exactly. A ding often leads to rust or a burr that will shred the seal. On my '07 V-Strom the stanchions were pitted and rusty. I called Catalyst Reaction in San Carlos (yes, I get it, overkill for a 'Strom) to see if they could fix my shock. I happened to talked to the owner and he passed on the work but spent around 15min giving me tips on how to DIY a repair. Very generous with his time and expertise so recommended. In any case, the most important tip after filling pits with epoxy and sanding and ready for reassembly, was to spray the shock tube with WD40 and don some nitrile gloves and run your fingers down the tube. The nitrile glove will snag on burrs and you can knock them down with high grit sandpaper.