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Fork Seals - K100

C

Carguz

Guest
How tough a job is a fork seal replacement on an '85 K bike?

Since, I'm painting, I have the fairing and everything else off the bike. Do I need special tools? Is it tough for a first time job? While I'm at it, I plan to replace pads. Any hints, tips, etc. much appreciated.

Carlos
 
How tough a job is a fork seal replacement on an '85 K bike?

Since, I'm painting, I have the fairing and everything else off the bike. Do I need special tools? Is it tough for a first time job? While I'm at it, I plan to replace pads. Any hints, tips, etc. much appreciated.

Carlos

Remove the axle and loosen the bolts going straight up into the bottom of the fork -AFTER - draining the fork oil.

With the bike on the centerstand the fork sliders will pull straight down off the fork tubes and just clear the damping rods before the sliders hit the floor.

I don't think that model has a snap ring above the seal but look carefully to make sure. If it does, remove the snap ring with snap ring pliers.

Then use a wide bladed screw driver to carefully pry the seal out - be careful not to gouge the aluminum bore. Clean the recess thoroughly.

Then drive the new seals into place. The factory tool is a seal driver with a shank that is the same size as the fork tube. Some folks have found white plastic pipe the right size and with a length of the pipe and a fitting have made their own.

If you are careful you can drive the seal flush with a piece of wood on top of it and then seat the seal in the bottom of the recess with a large socket that just fits the outside diameter of the seal.

They are actually quite easy to replace but just be careful prying and pounding.
 
Almost sounds like I can pull it off. The Clymer manual describes the whole fork disassembly process but it sounds like I just need to focus on the bottom leg of the forks. Any recommendations on the oil, type, quantity, etc.

Are the pads easy enough?
 
No. The newer forks (after 8/91) require that the seal come off the top of the fork tube. The forks have to come off the bike.
Check your manual.


:dance :dance :dance
 
if you don't have a socket large enough go to a hardware store and get an "electrical" pipe coupler that is the right size, I bought my last summer for about $2 and then tapped it in w/ a block of wood and hammer.
 
Hi,
It's no big deal to replace the fork seals on '92-later K75 bikes. Just remember you need to drain the oil, remove the nut at the bottom, then remove the entire fork tube and slider from the triple clamp. To install the new seal, you need to have the fork tube in the slider before you pound the seal into the slider. That's where the white tubing Paul mentioned comes into play.
 
I'll just comment a tiny bit - not to disagree with Paul, but I had way too much experience changing seals on my FYK..

I found it was easier to remove the fork tubes from the triple tree, and work on getting the bolt in the bottom out with the fork slider clamped in a vice (with soft-jaws.) The bolt is typically drastically overtightened by dealership employees who look at the size of it and decide to really honk it down. Problem is - it's a soft, shallow head special bolt, so trying to get it out by pushing up on it (and the bike teetering around) while the forks are on the bike usually results in simply stripping the allen recess out of it. Luckily - since it's soft aluminum - it's very easy then to remove with a large drill (I used a 1/2" bit) and the stub left in the bottom of the slider will then come out with your fingers. If you clamp the slider in a vice, you can then use an allen-driver in a 3/8" ratchet wrench, and if Godzilla didn't get too carried away - you might get it out intact. You only have to loosen two bolts in the triple-tree to get a fork tube out. Loosen them, and turn the tube and pull down. Sometimes a tap on the top will help get it moving.

I'd still suggest ordering:

- 2 of the special bolts. They're on realOEM or Max's for a part#. Having them on hand invokes Eilenberger's Law of Spares - and you won't need them. Not having them handy means you WILL need them.
- 2 of the crush washers that are under each bolt. They are undoubtably mushed beyond reuse - even if you can reuse the bolts.

And I'd suggest not draining the oil using the drain bolt because it likes to strip out of the fork leg. If it's not leaking - LEAVE IT ALONE - never touch it or loosen it. The oil will come out just fine when you remove the bottom bolt that holds the slider on.

The seal on an '85 has no snap ring above it - it's simply a press fit into the top of the fork slider. Find a socket that is larger than the seal to use when tapping the new one in. The old one can be pried out with a screwdriver - try not to bugger up (tech-term) the slider where it seats. There are special seal-puller tools that would make this easier, but for a one-time job, it's questionable if it's worth buying one.
 
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Paul;

Is the procedure the same for a 93 K75S??

I'm due for a change.

1992 and later (model year) bikes have the Showa forks instead of the Marzochi (sp?) forks on the earlier ones. The Showa forks have a bushings internal to the sliders and external to the fork tubes that inhibit the removal of the slider from the fork tube.

They do come apart if jerked on slide hammer fashion, but then tricky technique and special tools are needed to put it back together. So aftermarket manuals advise to get the seal out and slide it up off the fork tube. Then a 2 foot (or so) plastic pipe with an ID to match the fork seal OD is used to drive the new seal.

I suppose the Showa forks are theoretically "better" what with bushings and everything - but they were a huge leap backwards as far as maintainability is concerned.
 
K Bike Fork Seal Replacement

Dear Fellow K Bike Owners:

I have replaced the Fork Seals on my 88 K 75 and always removed the plugs on the top of the fork tubes before pulling off the legs. In that way, the spring pressure is removed. You will have to pull the top plugs anyway in order to put fork oil back into the forks.

Also, you may see a lot of sludge in the bottom of the fork legs. I always clean that gunk out before reinstallation.

Steve Littlefield
 
Snap ring

I have a 1988 K100LT. I have removed the slider from the fork leg. The seal is held in with a snap ring that is simply a wire in a groove. There are no :ears" in which to place a snap ring pliers. How is the best way to remove this ring? I can't get in behind it to pry it out and I am leary of using too much force. Any tips?
 
I had the best luck with a tool from the hardware store called a "cotter pin puller".

I can best describe it as looking like a screwdriver handle with a round shank that has a pointed end, with about the bottom 3/4 inch bent over to a right angle.

Then a small thin screw driver to pry one tip of the ring away from the tube wall allows the tip of the puller to go in, and then with a small pry you can walk the ring out.
 
Thanks, Paul. I was going in that direction with my latest attempt, but the only similar tool I had in the box was a pick with a 90 degree tip. It did not have the horsepower to lift the rig from the groove. I am headed out to get the tool you suggest. I have been adding tools to my set for over 30 years, but it always seems you need another one.
 
Thanks, Paul. I was going in that direction with my latest attempt, but the only similar tool I had in the box was a pick with a 90 degree tip. It did not have the horsepower to lift the rig from the groove. I am headed out to get the tool you suggest. I have been adding tools to my set for over 30 years, but it always seems you need another one.

My little 90 degree machinist's pick didn't have the horsepower either. It was after I broke the end off of it that I went to the store and bought the cotter pin puller.
 
Thread reboot.

I'm just fixing to do this job as part of my post-crash rebuild. Like a previous poster, I thought the Clymer procedure was a bit overkill. Glad to hear it's a straightforward exercise.

I'm replying here to put the post near the top where I can find it again when I need it in a week or two. I'll make up for my transgression by posting some photos while I do the job.

Thanks in advance to the MOA and the guys who have gone before. :clap
 
How about posting it to the K-bikes DIY/Tech Library ?

Those of use that have the newer forks would like a DIY post too.
 
I just did the first leg on my 1990 K75S. It was brutally straightforward. Note I had the legs off the bike - but as you will see - it would be equally easy if that was not the case...but you have to remove the fender, brake calipers, wheel and the bridge piece the ties the two legs together at a minimum.

Just so we're all clear on terminology. The forks consist of two legs. Each leg has a slider (the bottom part - painted black on my S) and a fork tube (the top part - chrome finished). The fork tube actually consists of a tube, with spring(s) inside and a push rod coming out - but because I did not disassemble the fork tube during this job - I refer to the entire top assembly as the fork tube.

1) Remove the dust boot - that's the hard plastic piece that protects the point where the fork tube and slider join. Eyeball that fork seal - it's right there, probably blue. Note the spring clip - it's just a wire made into a circle that sits in a groove. Don't touch it yet.

2) Loosen the allen head bolt at the bottom of the tube. That's the bolt you can not see if the axle is in place. In my case. the bolt was only moderately tight. I used a set of pliers to give me some leverage. I had to stick the long part of the allen key up into the hole and the short part of the key didn't give me enough leverage on its own.

3) Remove the allen head bolt (it's a few inches long) and the aluminum crush washer, and then drain the oil from the fork. There's only about 300 ml - just over a cup. No big deal. Compress the spring a few times and just shoot that oil out of there.

4) Pull the slider off the fork tube. That's right - separate the two, it just slides right off. Pour whatever remaining oil is in the slider out...and now fish the spacer out of your oil tray. The spacer is a aluminum cylinder about two inches tall. It has a base that is a little bit bigger diameter than the body - according to my Clymer manual, this wide base faces *up*

5) I cleaned everything up a bit here - but I didn't do the full cleanup just yet.

6) I then used a swiss army knife to carefully pry the circlip out of the groove - be careful - but it really isn't that difficult to remove it witout damaging anything. Don't let it go flying out and around the shop though eh?... although it's not under a lot of tension.

7) I used a flat head screwdriver and got under the old seal and prised it out. It did go flying a bit - no problem. Do be careful again not to damage any alloy - but you'd have to be really hamfisted to do that.

8) At this point I cleaned the slider inside and out with brakeclean. There was sludge inside so I shoved a rag all the way to the bottom using a long thin steel rod (thicker than a coat hanger, thinner than the bolt I removed at step 2/3) and then pushed it out again by poking the steel rod through the bolt hole. I did that a few times - each time worrying that I would screw up and scratch the inside of the slider - but I never did - because I would have to be really careless to let that happen.

8a) While I was doing this I left the fork tube to drain but nothing really came out. I also removed the fill plug at the top and turned it upside down to drain but still nothing. Then I cleaned the exterior (shiny part) with brakeclean.

9) I pressed the new seal into the top of the slider with my thumbs - that got it started, but it didn't get me very far - so I turned the slider upside down on a block of wood and using a rubber mallet I beat down on the bottom of the slider - thereby pressing the seal in so it was flush. But that's not far enough either so I used an old outer bearing race from the head tube to get the seal almost seated completely - but the bearing race was too big around so I still had a mm to go. I finished off seating the new seal as careful as I could with a drift and hammer - but I wouldn't recommend doing that because it's way too easy to deform the seal. I came damn close.

10) Once the seal was seated. I put the circlip back in using my fingers only, easy. I also lubed the inside of the seal with goop that I purchased when I bought the seals...it's described as fork seal lube and it is bright white in colour.

After this point I'm reassembling......

11) The spacer went in the slider first (big end up), and the bolt with washer (new if you have one) through hole in the bottom of the slider. Hold that together with a finger.

12) Insert the fork tube past the new seal into the slider - and then start the bolt. It helps to have the slider clamped in a vise here, but you can turn the assembly upside down too.

13) Torque the bottom bolt to whatever spec is in the book or, if you're like me, use the pliers again to administer exactly the same amount of torque to the allen key as you administered when you removed the bolt.

14) Reinstall the dust cap - or in my case - install brand new gators. That's pretty much it.

14) At this point I reinserted the finished leg into my triple clamp, which I have just finished redoing with new bearings as well. The top of the tube is 180mm from the top of the bottom clamp.

15) I will fill with new oil later. It's not entirely clear from Clymer how much and what type of oil to use in my S forks. That shouldn't be too hard to figure out though.

If all goes well I'll snap some photos when I do the second leg - and post them here. It really was dead simple to take these tubes apart. From what I understand though - they aren't all this easy.
 
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Marzocchii/Showa forks changeover in 1992

Wonderful DIY instructions for doing your '90 forks---thank you--- but just to be clear here you are talking about the Marzocchi forks and NOT the Showas used on all 1992 and later K75s, correct?

Paul pointed out earlier that it is a different and less easy method for doing the fork seals on the later models since they are constructed differently. At any rate, congratulations on doing it yourself succesfully and an otherwise superb write-up.
 
Hi Zagando - love the polished tank work you did. I'm going there (or close to there) eventually myself once I find a suitable candidate for conversion to cafe. I would have done it on this bike - since I just crashed it - but I need a touring/commuting bike with bags first and foremost, so I am bringing it back to stock specification.

Anyway - yes my instructions (and photos to come) are for the much much simpler early K forks, not the later Showa forks.

I note that this month's MOA ON magazine has a fork seal replacement article written by Paul Glaves. I think that article better represents the level of effort required to fix the Showa forks.

It's coming along...looking forward to maybe getting a ride in next month...
 
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