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

[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.

[McCabe-Thiele (Ted)]

The yellow spots are paint blobs marking where the seal line sits.


PXL_20241201_140255009 by Macabe Thiele, on Flickr

[Bryanj]

Yes they need sorting or they will rip seals

[McCabe-Thiele (Ted)]

That what I thought, at the moment some of the Superdream owners are fitting new Tubes fron China (wide variety of prices from £135 -£190 for a pair} others have gone for refurbs by hard chromers.

A firm named Marque Restore of Coventry have been recommended.

[Sesman]

Obviously you need to be very cautious regarding replacement fork tubes. I learnt this when buying replacement stanchions for my Norton Wideline forks. The quality, and  more fundamentally strength, can vary between suppliers.

Personally I’d choose hard chroming, assuming you can establish that the ones you have are originals. Is it possible to establish if the replacements on offer are equal or superior to what was fitted originally?

[McCabe-Thiele (Ted)]

Wemoto sell some more expensive ones, DS appears to have stopped supplying them. CSML price is at the very top end.

I think mine are original, there was no indication they have been taken to bits previously, the seals appear to be the original  they are RSA 33x4.6x11 replacements are listed as 33x4.6x10.5 everywhere I've looked.

[Sesman]

Mmm. Interesting one that, Ted. Let’s us know how you get on.

Out of interest, how does the cost of replacements from a known, reputable source compare with hard chroming. Another consideration is that the value and quality of hard chroming is well established, but is this the same for new replacements?

[Bryanj]

Dont forget Phillpots, they do a collection and delivery in the price plus rechrome the top nuts free, or at least used to

[Seabeowner]

Are these the kiddies?:
https://www.ebay.co.uk/itm/226466256244

You could give them a ring. I've had good dealings with them.

[McCabe-Thiele (Ted)]

I used Phillpots on the 500 they cost £240 all in in December 2022.

CSML £367.80 a pair plus delivery & any import duty.
Wemoto £241.76 Slinky Glide - product description reads very good.

GBKKRacing (China) £161 pair!!

Wemoto do a kit form with all the seals, can't find that price at the moment.

[McCabe-Thiele (Ted)]

Are these the kiddies?:
https://www.ebay.co.uk/itm/226466256244

You could give them a ring. I've had good dealings with them.

They dont appear to list the UK CB400NA plus my part number is different 51410-413-013 they are 33 mm x 581 mm.
Mine are the early type with no drain lug on the forg legs, they changed the internal design quite substantially on other versions.