Fork Oil on Dust Seal

[reddeviljp]

I searched but the other q's were not as specific as mine.

There is a light smearing of oil, picked up on MOT last month, on my left fork dust seal but nothing on the right-hand fork. As I'm stumped as to what the problem is and how to fix it I'm throwing over to you good lads and lasses.

1. What is the probable cause?

2. Will it become a problem as it is only a light smear?

3. How can I fix it if it needs to be fixed?
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Bike: 1993 CB400 SuperFour - 1999 Yamaha FZS600 - DAS passed 7/11/13 - Working my way towards a Yamaha FZ1.

[bugeye_bob]

your seal is failing, not sure why that is complicated,
How else do you think that the fork oil is getting out ?

[Itchy]

Fork seals are coming to the end of their lives.

You have two options:

#1 Change them and the bushes which will cost £10 per side in parts and £80 in labour from a mechanic* changing them involves putting the bike on a stand (or hanging it from roof beams), removing brake callipers + wheel. Undoing bolts on the top and bottom, then undoing the triple clamps at the top and bottom. Then pulling them out, then slide hammering, if it works it comes out if it doesn't it means heating them or sticking them in a vice and pulling them apart getting fork oil all over yourself taking the old bushes and seals off, gentling putting new ones on, filling with oil then reassembling them.


(*something I believe is worth it as I nearly impaled myself separating the stanchions from the fork legs)

#2 Ignore it, like I did, at which the fork seals burst while I was riding a fast twisty road, meaning no front brake. I then rode around with a bag wrapped around the top of the fork leg to keep the oil off my brake disc, eventually went to point #1 (do not forget to change the bushes too).
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Spain 2008France 2007Big one 2009 We all die. The goal isn't to live forever, the goal is to create something that will. In the end, your life will flash before your eyes. Make sure it is worth watching.

[stinkwheel]

Or there could just be muck/dust stuck under the fork seal. In which case you can get a bit of thin plastic (margarine tub lid is good) and shove it down between the seal and the fork leg to dislodge the dust and let it seal again.

Or you can buy a bit of thin plastic called a sealmate and do the same thing.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Rogerborg]

[reddeviljp]

It's not pitted and I've now got two photos, one of the good fork and the bad fork which I left with all the shit on it so that it could be seen on a photo. Normally it's very light oil.

[/img]https://i299.photobucket.com/albums/mm299/reddeviljp/Online/TheBadForkSeal.jpg[img][/img]

And the other side

[/img]https://i299.photobucket.com/albums/mm299/reddeviljp/Online/TheGoodForkSeal.jpg[img][/img]
____________________
Bike: 1993 CB400 SuperFour - 1999 Yamaha FZS600 - DAS passed 7/11/13 - Working my way towards a Yamaha FZ1.

[delsol]

The leaky fork, is that an hour's worth of oil, 1 day's worth of oil, 1 week or what, how often have you been wiping off the amount of oil shown in the pic?

Plastic shim pushed down between seal and fork leg may work, but I would like to know that I had not lost a lot of fork oil.

[Slacker24seve...]

The parts (seals and oil) cost buttons. If you can find a suitable seal driver (PVC waste pipe, massive socket etc) its not that hard.
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Banger rallies are ace

[Rogerborg]

Might as well have a go. Lift the dust seal up, run a strip of plastic around between the leg and the oil seal, wipe the leg down, bounce the suspension and see if there's still oil getting past. It's nearly as quick to do as to type.
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[Islander]

[TUG]

Just change the seal, cleaning the seal with a seal mate or other has never worked for me and the if a little bit of dirt has caused this much oil loss you're going to need oil anyway so what's the point? Just change the seal on that side or both it's a good day of a job if you're a noob or run into issues or a couple of hours if your hand with spanners.

There are plenty of tutorials online but if your going to DIY it then buy one of these:
https://www.motorcycle-superstore.co.uk/4844/i/motion-pro-fork-oil-level-tool

The reason: Although you might know the correct ml of oil to put in, there might be a few ml still in the leg and not putting to correct air gap in a leg will cause handling anomalies.

I must say that replacing your fork oil in both legs at once is the best course of action, it's cheap and will make your bike handle a lot better if the current oil is piss like.
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Haz ER-5, innit!

[Rogerborg]

[TUG]

[stinkwheel]

It has worked for me several times.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Islander]

And for me on several bikes.

[reddeviljp]

Thanks for all your helpful answers, folks.

When it gets to a nice, warm day I'll use the film down the seal trick that I've watched being done but if that doesn't work then I'll book it in at the bike centre and prepare for a few hours work changing everything.
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Bike: 1993 CB400 SuperFour - 1999 Yamaha FZS600 - DAS passed 7/11/13 - Working my way towards a Yamaha FZ1.

[TUG]

Well I don't know then, maybe the seals I replaced where definitely fucked? But it has never worked for me that trick, not even once.
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Haz ER-5, innit!

[Vincent]

How many people replace the dust seals when doing the oil seals? If dirt's getting behind the oil seal from above, I'm guessing the dust seal is past its best?

Other reasons apart from worn seal for leaking:

Worn bushes. These are normally two teflon coated collars that fit on the outside of the lower part of the stantion. One near the bottom, and one just under the seal. They provide a "snug" fit for the stantion to slide inside the fork leg and wear over time. Replacement requires splitting the forks which can be a bit awkward.

Too much oil or air. On air assisted forks, they usually have a small amount of pressure. Some folk pump them up like a tyre
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[Jim Mc]

Tips for repairing pitted forks? Have read a variety of methods online but mostly american products. Also doesn't explain how you reapply the PTFN coating when they talk about sanding down etc.

[davebike]

Only real cure for pitted forks is new stanchions or your ones re-cromed not cheap
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[Islander]