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Front forks Gaiters/Dust Seals/Oils double lipped seals discussion/question?

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McCabe-Thiele (Ted):
The front sliders on my Superdream are a tad pimply where they meet the oil seal stretching an inch or so below the seal to around three inches above. When I drained the forks by inverting them when removed (no drain plugs on the 400NA) the amount of oil that came out was pretty much the same as the fill volume of around 140 cc in fact I think there was more  than that.

The bike was fitted with fork gaiters by a long term owner in Aug 2019  at 50,646 miles as evidenced by a raft of invoices that came with the bike from a repairer. The Mot history from 2011 (49,224 miles) to 2017 (49962 mles) shows the bike only covered some 538 miles covered in that period. The bike has only covered 32 miles since Aug 2019 when the gaiters were fitted, (assuming no clocking) presumably as the sliders were showing some pimplin/rust.

The fork gaiters were in pretty poor condition consistent with uV degredation, one gaiter was holed near the bottom the other had split.

The fork stanchions are in pretty good condition inside so I'm looking at what to do about the  pimply sliders. Hard chroming is not cheap, aftermarket  available at a lower cost. That had me thinking just what do the double lipped seals actually do in terms of keeping the oil in place. It appears to me in my ignorance that the dust seals or gaiters main role is keeping water out, will some pimpling actually let oil escape or is it more about keeping water & dust out?

A replacement pair of gaiters or dust seals might be fine for several thousand miles. I don't want to spend money where it's not needed bearing in mind my mileage will most likely be less than 500 miles p.a.

Just how much foaming oil do the double lipped seals actually stop from escaping?

Bryanj:
In theory all of it Ted the top seal scrapes crap upwards, the bottom one oil downwards

McCabe-Thiele (Ted):
With the relatively small volume of oil inside these forks I was trying to figure out how much oil is trying to escape up the sliders onto the seal areas.  How bad does slider pimpling have to be to cause oil loss past the seals?

The engineer in me says it needs sorting by replacing the sliders (cheap ones available from China), the miser side says just fit fork gaiters again then see if they leak oil as there did not seem to be a shortage of oil on dismantling. That said it's not done much mileage since the gaiters were fitted.

Bryanj:
I assume you mean the chromed tubes or stanchions rather than sliders Ted, the sliders are the bits the wheel bolts to.
Pimpling, or pitting, of the chrome tubes makes it rough and the sharp edges tear the seal lip letting oil out.
At MOT any oil leak is a fail so even with gaiters if oil is visible its a no no.
There is a rough and ready sort of fix for pitting.

1 polish the tubes with fine wet and dry where the pitting is

2 warm up the tubes with a plumbers type torch(i use the gas canister type) to boil all the residual oil out

3 mix up some araldite, rapid will do, and smear it into the pitting

4 when dry re polish with the wet and dry tillsmooth again

This will last a few years if lucky until you can afford  new .

Due to the few miles this will bo with you Ted this will be fine for you in my opinion

McCabe-Thiele (Ted):
Yes Bryan  I mean the fork tubes I never know what to call them.
I only know the other bit that holds wheel & mudguard as a fork leg, som is a tube a stanchion?
I can see they slide up & down the fixed bit so sliders & tubes from now on.

The pimpling is very fine I will pop a picture up in a bit.

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