Replacing Fork Seal (oilhead)

[B-art]

That rusty wacher is more common than you think, it is because of the water passing the seal while traveling up and down.
Brush the wacher with a wirebruch and re-use.
But do clean the inside of the inner and outer fork leg, change the oil. Oil is hygroscopic (do you spell it like this?), and must be changed every ????km(see manual) to prevent damage to the fork.

Honing is not nesesery becaus the glyding buches are teflon coated->softst part.

B-art

[kevbo]

I'll reiterate that I still had leakage with two new seals,
fixed it by polishing even though the fork leg LOOKED and felt fine.

[Carlos M]

I guess I should have RTFM in the 1.st place... permissible runnof is 4/10 mm so I should be inside spec.

I'll give the tubes a good polishing session and I'll replace the dust cups also. Hope it will hold.

If any of you disassemble your front fork for seal replacement I would be curious to know the runnof you find.

[kevbo]

When I polished mine on the lathe, I grapped the upper hex with in the three-jaw, and made a butt plug for the live center to run in.

I doubt there was as much as .005 runout, and most of that was at the chuck end, so ecentric chucking or hex rather than a bent tube.

[OUtback UFO]

an additional thought about replacing the fork seals.

put a but extra grease on the inside of the dust cap... this will help catch dust more if it gets inside the dust cap to help lessen wear on the seal.

[DRTBYK]

Said OUtback UFO:
an additional thought about replacing the fork seals.

put a but extra grease on the inside of the dust cap... this will help catch dust more if it gets inside the dust cap to help lessen wear on the seal.

Seems to me that this would just hold all of the dirty that makes it past the dust boot and potentially casuse greater ware on the inner tube over time.

[sashapave]

thanks for the photos! neat trick with the piece of metal for screwdriver prying! beats using the top of the fork.

on the 1100 it's not too difficult to do the job with the forks still mounted. in fact, if you're good prying out the old seal, then it can be a 20min job easy.

a big washer and socket makes the re-insertion easier. just tap it in till it stops, you'll feel it.

i screwed up and put too much oil in when i replaced mine, which meant more leaking. removing the extra oil with a fuel line worked great.

how important is it to change the oil completely? i mean, it's really only used for lubrication and not dampening isn't it?

-s

[OUtback UFO]

Said DRTBYK:
Seems to me that this would just hold all of the dirty that makes it past the dust boot and potentially casuse greater ware on the inner tube over time.

That is what a BMW mech recomended to me. I ended up needing to replace the Shinny male part of the fork due to a major scratch from heavy off roading. I know have the Touratech boot covers. the extra grease did help as the mech said it woiuld. Though it is a though for those that live in high dust areas. It did help to keep the nasty granite dust from the Yukon from wearing out the seals on the ride back from AK this May

[Carlos M]

Hi,

Thanks for the tips guys. The grease under the dust cup is common practice on dirt bikes (real ones, that is). But the manual of my KTM says to put new grease in every 15 riding hours! So, I guess it is a good thing to do if we do ride off-road, but it should be at least inspected on a regular basis (like monthly?)

I borrowed a friend's micrometer and built a pennytech measuring stand:





As expected, the tubes are more or less inside spec (0.016")regarding runout. (one is at 0.015" and the other at 0.018"). I'll keep them as they are, and will reinstall after a good polishing.

[bemiiten]

From my experiance, as long as the innertube slides freely in and out of the outer tube by hand, I would not sweat the small amount of runout you have.

[johnjen]

One additional note for all of you that have done this... No one mentioned bleeding off the air pressure from the re-assembled front forks... That will change the handling considerably... Just a thought..

JJ

[Markus Derailius]

Originally Posted by johnjen

off the air pressure from the re-assembled front forks
JJ

jj...pm'D YA

tRYing to figure out exactly how much to bleed out of the forks....also can you do this fully assembled?

[Guzz]

Originally Posted by johnjen

One additional note for all of you that have done this... No one mentioned bleeding off the air pressure from the re-assembled front forks... That will change the handling considerably... Just a thought..

JJ

Yeppers, I just don't know if one is supposed to do it with the forks compressed, extended, hot, cold, etc. I asked the dealer, and couldn't get a firm answer.

[bemiiten]

Originally Posted by Guzzler

Yeppers, I just don't know if one is supposed to do it with the forks compressed, extended, hot, cold, etc. I asked the dealer, and couldn't get a firm answer.

Bleeding is not nessasary. The small amount of pressure that gets traped when the tubes slide together should have a minimal efect.

[Guzz]

Originally Posted by bemiiten

Bleeding is not nessasary. The small amount of pressure that gets traped when the tubes slide together should have a minimal efect.

Well then why does the shop manual say to do so?

BMW Shop Manual Page 31.9]
• Install fixed tube.
• Install washer (6).
• Push the lightly oiled shaft sealing ring fully up to
the stop on the slider tube, then press home by
tapping lightly and using threaded bush,
BMW No. 31 5 611, expander,
BMW No. 31 5 612, and reducing adapter,
BMW No. 31 5 613.
• Install retaining ring and dust wiper.
• Insert bleed screw (1).
• Bleed telescopic forks under zero load.

Curious...