I recently changed a fork seal only to find the new one leaked, as did the second .

Everything was clean prior to fitting, I used cling film top of the leg to protect the new seal .

A seal driver tool was used to fit them.

Seal lube applied  but both leaked .

I then ordered a set from a different, well known uk  supplier, and this time all is good.

The seal from  the second set did feel more resistant when sliding it down the fork leg, 

 both sets were marked 41.4mm , perhaps my bike prefers blue seals rather than black ones.

Bob

There was a certain brand of seal that was renown for leaking, I can't remember the brand. I've had my current seals for nearly twenty years. I fill under the dust cap with heavy silicone grease which seems to have worked and lengthened their life. I change the grease every couple of years or more often in dusty conditions. Other Brickers have had success with a tool called Seal Mate which can clean out any crud under the lip. you can save money and make one out of the side of a plastic soft drink bottle.
Regards Martin.

audibob wrote:I recently changed a fork seal only to find the new one leaked, as did the second . . . .  both sets were marked 41.4mm

Was it an OEM seal?

My tubes measure 41.4mm  

My leaky black seals came from Motorworks,  the blue seals are from Motobins.

Bob

audibob wrote:My tubes measure 41.4mm  

That seems to be measurement alright.

I've recently recommissioned an old K100.
I replaced the fork seals (from Motorworks), and cleaned out the forks as a matter of course.
They leaked straight away. So I got another pair of seals from Motorworks, this time they were ok for a hundred miles or so, and now they are both leaking again.
I've not had a BM before, and it seems a bit strange that the seals aren't held in with a circlip or anything!
Are you saying seals from a different supplier may solve the problem.
I will add, that the fork legs are in good condition.

Measure the diameter of the forks they could be K75 which are 0.4mm smaller. As far as I know all the K100s had circlips.

RicK G wrote:Measure the diameter of the forks they could be K75 which are 0.4mm smaller. As far as I know all the K100s had circlips.

My fork legs measure 41.4mm

I believe the that the Fichtel & Sachs (K75C and K100 (not 4 valve) forks were 41.3mm diameter, and the later Showa forks K75 08/91 - 1996 were 41mm diameter.

Update: Looking at the MAXBMW parts list site, the snap ring to retain the seal was fitted from 09/87.

Mike

mike d wrote:I believe the that the Fichtel & Sachs (K75C and K100 (not 4 valve) forks were 41.3mm diameter, and the later Showa forks K75 08/91 - 1996 were 41mm diameter.

Update: Looking at the MAXBMW parts list site, the snap ring to retain the seal was fitted from 09/87.

Mike

Thanks Mike.

Mine is an 84 K100RS, so it appears to be correct.

I just need to know if there is a 'better' make of seals for it. In the UK.

Tim

I use ATF in my forks. Cheaper than fork oil, and it has stuff that softens the seals a bit so they work better.

Were the seals from Motorworks OEM or pattern.

If pattern, I would look to buy genuine OEM seals.

Mike

If you pack heavy silicone grease between the seal and the dust cover it will prolong the life of the seals. Clean and change the grease every couple of years. It stops road crap from getting down to the lips of the seals and keeps them lubed. I last changed my seals over 20 years ago. Silicone grease packed under the boot of your rear master cylinder will also extend it's life. It'll stop the ingress of water and road scum.
Regards Martin.

I have had very limited success with any of the aftermarket seals but genuine OEM have always been good. Check the fit of the two parts as 35 years can show some wear. If there is wear the only option is replacement. Also check for tiny rust pits on the moving surface as that will cut a seal to bits in no time flat.

Forks used in K's ;

RicK G wrote:I have had very limited success with any of the aftermarket seals but genuine OEM have always been good.
Check the fit of the two parts as 35 years can show some wear. If there is wear the only option is replacement. Also check for tiny rust pits on the moving surface as that will cut a seal to bits in no time flat.

I’ve ordered some OEM seals from Motobins.
The chrome on the legs is good, but I will check the slider to leg fit.
Thanks for the help.

And gaiters always  fit gaiters (as you will have the forks apart anyway.

Otherwise, even with the OEM seals, they will eventually leak again. 

Since fitting gaiters, problem went away.

Corkboy wrote:And gaiters always  fit gaiters (as you will have the forks apart anyway.

Otherwise, even with the OEM seals, they will eventually leak again. 

Since fitting gaiters, problem went away.

+5 (the number of bricks I've put them on)  No leaks so far(knock on wood).

They also help in the BMW "look" of the bike by hiding those shiny fork stanchions.

And do NOT use aftermarket ones. They won't last. Yes, they're half the price (or less) than OEM, but last less than a tenth of the time.