Fork seals: what am I missing?

[El Thermidor]

So I'm soon to be fitting my third fork seal in as many weeks to the LH leg. It's not a hard job, but it's getting a bit boring. So before I do, I thought I'd ask if anyone else has had repeating issues with these weeping, and what I might have missed...

- I'm using genuine, main dealer seals, bought at different times so shouldn't be a batch issue (the first one was bought a while ago)
- I've followed the excellent Steptoe instructions
- The stanchion looks clean and straight, no evidence of corrosion spots (in the swept area, anyway)
- The seal is installed so the small notches are up (the side that would hold more fluid is down)
- There is a small vertical scratch on the seal seat (previous evidence of ham-fistedness): I've smeared this with blue Hylomar to help it along, but is this enough / is there something better? It has sealed with this present before
- Each time the fork leg and seal have been lubed with fork oil for assembly: just a smear, and it can't be this that I keep cleaning off the back of the fork leg
- I think I'm being careful enough installing the leg and not nicking the seal anywhere

Am I being daft, or just really unlucky?

 

[Cortina]

Too much oil in fork leg ?

As you probably know the oil in here does not really do much

drain and refill with correct qty to be sure (as you can change seal without disturbing much ... and do you really know how much is in there ??)

 

[Slipperyeel]

There's no need to lube the station before you reassemble.... In fact I wouldn't do it. The polished face of the stantion is sufficient. I haven't done this job on the beemer but plenty of times on conventional forks and always just slid the new seal over the stantion dry....

Not sure if lubing the stantion first is the cause of your problem but worth noting when come to doing it again (for the last time I hope! )

Sent from my GT-N7105 using Tapatalk

 

[Grizzly]

Fork Leg Alignment - Parallel?

Hi there,
All you sure your fork legs/tubes are perfectly aligned - Telelever forks are a bit strange and if too many screws have been slackened at the same time it can allow the forks to be re-secured with a slight twist - putting strain on the bushes and seals.
I tried to explain my method for aligning/securing and checking on another post recently - link below. It's a bit long-winded, but it's not the simplest task to explain
This may not be anything to do with your problems - but have a read - might be worth checking over alignment.

www.ukgser.com/forums/showthread.php?345728-Fork-alignment-and-bleeding&highlight=fork+alignment

Cheers...................Grizzly

 

[ianboydsnr]

You letting the air escape when you get the bike back on its wheels, the air is trapped as you fit the bottoms, and it needs to come out or it blows out with oil past the seal?

Anyhow the oil in the forks is only to lube the chrome tube, so just keep drying it until it stops doing it!

 

[(RIP) Bin Ridin]

I put seals in upside down, had mystery leak, redid rightwayoop and all was good. Worth checking...

 

[El Thermidor]

Thanks all for the suggestions. I ran the bike this weekend without the dust cover and it does appear it's blowing between the stanchion and the seal, and not between the fork lower and the seal (where I originally thought).

- There is the possibility of too much oil, but I've never changed it or added any, and it was fine for some years, so I was kinda hoping it'd be ok - if anything not quite enough. I figured there was more chance of not fully draining and therefore overfilling if I changed it?

- Fair comment on the not lubing the seal before reassembly. It was something I've always been taught to do but can see how it could be causing a problem. Will refrain next time.

- Fork alignment: not thought of that. Is there a way of checking without disassembly? I've never had them apart, so it's unlikely but worth assessing if non-destructive.

- Air in forks: I've let the air out when the bike's on its centre-stand, which appears to be the method in Steptoe's instructions. I'm not sure the difference is substantial, but am willing to give it a go.

- The photos showing top and bottom are the only ones missing from Steptoe's instructions, but looking at the others (and elsewhere) it would appear the side with half a dozen tiny intendations round the edge is the top, and the side that looks "deeper", i.e. could hold more fluid if filled, is the bottom. Please tell me that's right...

The MoT is due soon, and while I can bodge it through by draining the oil (thereby removing evidence of the leak), even the cowboy in me doesn't think that's a good idea.

 

[Shunt]

A trick for the mot is to lift up the dust cover.
Roll up a bit if toilet paper an wrap it lightly round the stancion on top of the oil seal.
Then set the dust seal onto it.

 

[ahutcheon]

I can't remember which is bottom and top on the seals - I matched up against the way they came out and everything worked fine. Given that seals are cheap (might even come out in one piece and go back in if they're new?), I think you owe it to yourself to rule out the "wrong way up seal" possibility.

 

[Grizzly]

Bleeding

The forks should be vented with the weight of the bike and rider loading the suspension - ie suspension as it would be on the move - NOT on the centre stand.
The way I check for alignment/twist during assembly is to sight down the front edge of the TOP yoke and try to visually align that edge with the two points where the stanchions enter the BOTTOM yoke - makes sense once you read it a few times and try it
It's not a method to seriously check for damaged/bent components - simply to check everything is/was naturally aligned during re-assembly of stanchions in bottom yoke etc.

Cheers........................Grizzly