Fork seal saga

[Pykie]

Hi,

I seem to have got a bit of a never-ending story going on with me fork seals.

About 8k ago i changed my forks and dust caps. New BMW items from motorworks. I changed the oil at the same time as the right had been leaking for a while and the leg was full of gunge.

Over time the right leg developed a slight tide mark, and I decided to be good and change the seals for the MOT instead of just wiping the stanchion.

This time the new seals I got from Motorworks were different:
The 1st set supplied were the same as removed - directional multi-lipped seals as used on most forks.
The second set seem to be bi-directional, as there are 2 lips, one facing down and one facing up, both with springs.

I needed to use the bike the next day so I checked the sizes, pulled out the old seals and replaced with the new ones. They were more-or-less symmetrical, so I put them in writing upwards/outwards as usual.

I inspected both stanchions: the right had a very faint scratch which i dressed back slightly, and I swapped the stanchions left-to-right to see if the scratch was an issue.

Both seals lasted long enough to pass the test, but are now leaking and getting worse.

I have changed a number of forkseals in the past (not on BMW's) and never had problems, and am fairly confident that I haven't ballsed the job up.

I called motorworks this morning, who said that they supplied genuine parts on both occaisions, and the bloke seemed baffled.

So, my feeling is that the seals are wrong - has anybody had something similar? Is there a parts supersession? What? Eh?

Any suggestions?

Olly

 

[bowser]

are you sure you havent put to much oil in, as I understand it the seals do very little, there is no suspension handled by the forks the oil is just there to lubricate the stantions, all the suspension is provided by the single front shock, I dont think it would even be a failure for the MOT if it was leaking, it only fails on the standard type because the oil forms part of the suspension system in that the oil provides the damping.

 

[davegs]

Seals

As above, but why not put a pair of rubber gaitors on? think mine came from
an 80 GS, even if it don't leak it keeps all the shit out and oil in and no one sees leaks but I reckon you've put to much oil in they are NOT normal tellies
so have a good look.

 

[Pykie]

No, I have got the right oil level, I know they are not normal telescopic forks and I dont want to fit gaiters. Thanks for the interest tho.

What I'm trying to find out is have I been sold the wrong seals or did BMW change them for a new type?

Incidentally, I dont really see that the forks are all that special; the legs, stanchions and seal set up (and the original seals) are just like a set of normal forks, all thats different is that there is no valve block or spring in it, so the seals should do exactly the same job as they do on conventional forks.

So.... why are my new seals different? Is that why they don't seem to work properly?

 

[monkeyboy]

just a simple thought so don't shout Did you open the bleed screw when you put the sliders back in? If you didn't you might have a bit too much pressure in the forks and that might push oil past the seals.

 

[rudiemoto]

what air gap

how much oil

what type of oil /5w 10w so on

did u rubber lub the seals

r there in the right way

if all the answers r right
post a pic of the damaged leg

 

[Pykie]

First off, my apologies to Bowser and DaveGS if my reply came accross as a bit snappy, it wasn't really meant that way. Thanks for your help.

Second,
Air gap? Dont have a spec for that, so don't know

How much oil/what wieght? 450ml of 10wt oil per leg as Mr Haynes specified

Air pressure equallised using bleed screws? Yes

Rubber lubed seals? Seals lubed with fork oil before inserting fork stanchions

Seals right way up? Yes. Must be. I had a look at Steptoes fitting guide again: the photos show a seal similar to but not identical to the ones I was sent, the same way up as I fitted them.

Damage to fork stanchion? I tried to take a photo of the scratch with the forks assembled and couldn't even find the scratch. I don't think that was the culprit, especially as both seals leaked.

Went to a local shop today and bought a pair of cheapo Kenoco (or something like that) seals today for 12 quid, fitted them and went for a (admittedly not very long) bumpy ride.

Perfect. Not a trace of misting of the chrome stanchions. Its a bit too soon to say, but I reckon they might work.

Despite my grumpy response, I now reckon gaiters might not be such a bad idea......

 

[CHANGELING]

MZ ETZ 250 gaiters fit well too ! I know pennytech.