Page 2 of 2 FirstFirst 1 2
Results 16 to 29 of 29

Thread: Fork Seals - K100

  1. #16
    Registered User jwetering's Avatar
    Join Date
    Aug 2011
    Location
    north vancouver
    Posts
    141
    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.
    jasper
    north vancouver

    1990 K75S

  2. #17
    Registered User argent brick's Avatar
    Join Date
    Aug 2012
    Location
    Wine Country, Northern California
    Posts
    461
    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.
    Lynn
    MOA #57883
    Current Ride: 1995 K75 Standard
    Past: 1978 Yamaha XS 750, 1976 BMW R60/6

  3. #18
    Registered User jwetering's Avatar
    Join Date
    Aug 2011
    Location
    north vancouver
    Posts
    141
    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.
    Last edited by jwetering; 12-19-2012 at 08:48 AM.
    jasper
    north vancouver

    1990 K75S

  4. #19
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085

    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.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  5. #20
    Registered User jwetering's Avatar
    Join Date
    Aug 2011
    Location
    north vancouver
    Posts
    141
    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...
    jasper
    north vancouver

    1990 K75S

  6. #21
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    Very good, Jasper; thanks for the mention of Paul's article in ON. Good luck on getting your bike back in rideable shape sooner than later. Once you are ready to polish your tank I'll be glad to give you some pointers (stock up on lots of elbow grease as it's quite a bit more work than one might imagine). It is worth the effort, though, way beyond all the compliments you'll receive once it's not hiding under paint.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  7. #22
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    3,327
    Quote Originally Posted by jwetering View Post
    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.

    .

    I use 290cc of 7w in each fork for the pre-92 "S" forks.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  8. #23
    Registered User jwetering's Avatar
    Join Date
    Aug 2011
    Location
    north vancouver
    Posts
    141
    Quote Originally Posted by 98lee View Post
    I use 290cc of 7w in each fork for the pre-92 "S" forks.



    Thanks Lee - somehow in the back of my mind I knew you'd have the answer.

    Your parts have arrived in the meantime - Thanks !

    It seemed like they were packed for a trip to the centre of the earth.

    I now have a full complement of marakesh parts...although both side panels do need some work. I'm going to have to find somewhere in Vancouver where I can get a colour matched rattle can made up.

    Hopefully I'll get back at it today.
    jasper
    north vancouver

    1990 K75S

  9. #24
    Registered User argent brick's Avatar
    Join Date
    Aug 2012
    Location
    Wine Country, Northern California
    Posts
    461
    Quote Originally Posted by jwetering View Post
    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.

    Thanks for a great write up. To bad it was not for the newer style forks, but we do have Paul's Article. BTW, which gators did you use?
    Lynn
    MOA #57883
    Current Ride: 1995 K75 Standard
    Past: 1978 Yamaha XS 750, 1976 BMW R60/6

  10. #25
    Near Balto. MD
    Join Date
    Jan 2007
    Posts
    24
    Great thread.....really helped me as I'm doing the fork seals on my '90 K75s. I also am planning on installing fork gaiters (the rancho shock boots). Regarding the gaiters, I wonder about the possibility of water getting in them and eventually contaminating the oil in the forks. Should the tops of the gaiters be left "open" or should they be sealed around the upper fork tubes?
    1990 K75s

  11. #26
    Registered User jwetering's Avatar
    Join Date
    Aug 2011
    Location
    north vancouver
    Posts
    141
    Hi guys -

    So - I have a story to go with the last few days wrenching. It's not particularly pretty - but it ends well.

    First the gators - I ordered mine from moto-bins. I don't know who made them - they only say Made in Italy on them. They seem really good quality though. The top end is a very thick section of rubber that fits very tightly on my fork tube. There is no need to clamp them. If yours don't fit tight, then I would think you absolutely would want to clamp them.

    I wondered how to attach them at the bottom. At first I pulled them just over the top of the slider - onto the lip which the normal boot fits on - and then zap strapped them tight....but I could see them easily slipping off while riding, so I pulled them *over* the lip, onto the body of the slider itself. I'm pretty sure they'll stay put now, especially since the bridge that ties the fork tubes together is acting as a bit of a clamp. I might still zap strap them. A picture of the gator tops should be attached.

    So - on to the story.

    After my total success on leg one - I move on to leg two with full confidence. Everything is fine until step 2, when I put the allen key in the bolt and it just spins around. Someone had torqued it so hard that the socket of the bolt had stripped. Argh.

    I get out my dremel, and try to cut a slot in the bolt head but (a) the bolt is very hard so my dremel bit just bounces off and (b) that sucker is so horribly recessed that it's impossible to see what you're doing and it's just so hard to get in there at all. I try again with a high speed drill bit and my cordless drill - but same thing.

    Finally I go to Canadian tire and purchase a set of easy out screw extractors - finally success - but the bolt is of course toast.

    No problem right...I have two spare bolts in the old fork tubes which were bent in the crash.....well not so much. On the first tube I try the bolt is deadly tight and the allen key starts to strip the head as well. So I use the smallest screw extractor in the hole that is recessed inside the allen socket (if you look at the bolt you'll see what I mean). The extractor gets a good purchase and - crack the bolt starts to spin...except it's not coming out. Then I pull on the fork tube and it comes right out of the slider - minus the push rod - which is still bolted to the slider and recessed so far there's no way I can get a hold of it. Total fail - and oh yeah about 300 ml of fork oil (seemed like more actually) spill all over the floor in front of my bench.

    So - I clean that mess up and try fork number two. This time I drain the oil out before I start, using the proper drain plug.

    The allen wrench isn't working either - so I go straight to the screw extractor. This time the screw starts spinning - again without coming out - but the fork tube doesn't come out either. The push rod is just spinning around inside the fork tube...and herein lies the greatest risk when taking the early fork tubes apart. There's little to stop that rod from spinning inside the fork tube.

    So on day two I hit the road to find a bolt that is the correct size and hardness - and the local Suzuki shop came through. In fact the finish on the bolt I got from Suzuki isn't the same as the BMW bolt. It had a matte finish while the BMW bolt looks to be cadmium plated - it's shiny at any rate.

    I did order the correct bolt from BMW and it's on the way. At the moment I am using the Suzuki bolt to hold it together. I waned to keep things moving ahead. When the BMW bolt arrives I will replace the Suzuki bolt...this will be possible with the forks installed so long as I don't put oil in them and I don't install the wheel.

    Anyway - success in the end but it was painful work.
    Attached Images Attached Images
    Last edited by jwetering; 12-25-2012 at 03:34 AM.
    jasper
    north vancouver

    1990 K75S

  12. #27
    Near Balto. MD
    Join Date
    Jan 2007
    Posts
    24
    Thanks for the info and the pic! That definitely helped. Bummer about your tale of woe but at least it worked out in the end. In my case the bolts on fork bottoms came out ok but if they required any more force I probably would've stripped the recess.
    1990 K75s

  13. #28
    BMW uber alles! Zagando's Avatar
    Join Date
    Apr 2007
    Location
    Rockport, TX
    Posts
    1,085
    On the brighter side your new fork boots look dandy; the ones I got from kbikeparts (Drake in Seattle) are OK but not as slick. They require clamps at the top and might also benfit from clamps or cable ties on the bottom as well. FWIW the kbike ones were only $28; imagine yours were a bit more.
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  14. #29
    Registered User jwetering's Avatar
    Join Date
    Aug 2011
    Location
    north vancouver
    Posts
    141
    Quote Originally Posted by Zagando View Post
    On the brighter side your new fork boots look dandy; the ones I got from kbikeparts (Drake in Seattle) are OK but not as slick. They require clamps at the top and might also benfit from clamps or cable ties on the bottom as well. FWIW the kbike ones were only $28; imagine yours were a bit more.
    Just checked - mine were 18 GBP - UK pounds that is - for the pair. I think the exchange is 1.6 these days so $29....

    All in all I've been pretty pleased with the price and quality at Moto-bins (hope I'm not pissing mods off here ). I only paid $60 for a complete clutch kit last year too. They don't have everything though...I had to go t Max BMW for a few o-rings and other bits that Moto-bins didn't have. They were fabulous as well by the way. I coulda-shoulda-woulda just used them for everything....although then I might not have gotten the cool gators.
    jasper
    north vancouver

    1990 K75S

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •