LC4 Sprocket seal replacement...

Discussion in 'Thumpers' started by creeper, Oct 29, 2005.

  1. creeper

    creeper Still alive...

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    How to replace a leaking sprocket shaft seal and O-ring in a KTM LC4.

    First, a view of the issue. It's not leaking profusely, but enough that you know if you leave it alone for awhile, it will turn into what rapiti calls his "automatic chain oiler"... and not a very good one at that.

    [​IMG]

    The parts you'll need are:

    Sprocket shaft seal.

    Spacer O-ring.

    [​IMG]

    Sprocket bolt kit or nut. This is an option... YRMV.

    Sprocket spacer. This is the part the seal seals against, it may or may not be reusable but you won't know that until you have removed it.

    The tools you'll need are:

    Basic hand tools

    Torque wrench, capable to the value of the fastener.

    Seal puller. I know most folks don't have one of these. They're not terribly expensive and can be purchased at some auto parts stores. Alternatives are a screw-in slide hammer type puller, like those used in body shops, or a lever and fulcrum arrangement that you'll have to come up with on your own.

    [​IMG]

    Sealant. This is another option. On older bikes that may have had their seals replaced a few times, the crankcase bore may be scarred and in need of a sealant.

    Some sort of cleaning solvent, paper towels, clean rags... you know the drill.

    Disassembly and seal removal

    Before you remove the sprocket, clean the area of large chunks of dirt, gorp and deer parts; don't want any crap sneaking in to your sprocket shaft bearing when you're not looking.

    After you remove the sprocket, clean the area again to remove any residue; then remove the sprocket spacer and O-ring.
    Clean the spacer thoroughly and inspect it for any grooving. If it seems excessive... it probably is and should be replaced.

    Mine looks pretty good; more of a polish than any measurable grooving.

    [​IMG]

    Use what ever tooling you've come up with to remove the seal. Don't pry against the crankcase bore edge... you will regret it later.

    [​IMG]

    Now that the seal is out, it's time to clean again. Do not spray solvent directly into the bearing seal cavity, instead wipe the area as thoroughly as possible with a solvent soaked paper towel or clean cloth. If you intend on using a sealant on the outside of the seal, it's very important that the bore it presses into is clean and dry.

    [​IMG]

    Installing the new seal and O-ring

    I don't have a fancy seal press tool that would allow you to install the seal by tightening a nut on the shaft... for that matter, I don't think one exists outside of maybe a factory KTM workers tool box. Maybe Loaded might whip one out on his lathe one of these days. :evil

    I use the super-econo, ultra-cheapass method of using assorted PVC pipe fittings as seal drivers. This seal is not that tight of a press fit, so they should do the trick.
    The seal measures approximately 1 7/8" in outside diameter... so you 'll need a driver that measures at least 1 15/16" to 2 1/4".
    Try and find something that is larger in OD than the seal itself, so that when the driver bottoms out on the case all around its circumference, there will be a good chance that the seal is square in the bore.
    The most important thing you have to consider when replacing a seal is that regardless of how it is installed, it must be installed straight, and flush to slightly below flush.

    [​IMG]

    Lightly oil and install the new O-ring onto the shaft and make sure it is fully seated.

    [​IMG]

    Wipe a small amount of clean oil onto the seals sealing lips and insert the spacer into the seal. This will act as a guide to center the seal and aid in holding it square to the crankcase.
    If you have some scarring in the crankcase bore, apply a small amount of sealant to the outside diameter of the seal and slide the whole assembly onto the sprocket shaft. Most of the sealant will squeeze out when you drive it in... that's OK.

    Carefully drive the seal into its crankcase bore; checking it frequently to make sure it stays square and true. If it appears to be cocking at all, tap only on the high side to square it up again.

    Here's the seal about a third of the way in... a touch crooked, but easy to correct.

    [​IMG]

    This is not a race; there is no time limit on getting this done properly. Chances are that if you wank the seal up from getting in a hurry, it will take longer to go buy another one than the time it would have taken to install it successfully in the first place.
    These seals have a steel shell, if you get heavy handed or don't pay attention to the job, you could damage the crankcase bore... then you are well and truly screwed.

    And we're almost done.

    [​IMG]

    Again, if you feel you need to, wipe the area clean and apply a thin film of sealant to the seam between seal and bore.

    So... our new seal and 0-ring are in place, we can reinstall the sprocket.

    I've known a few people that like to smear a gob of sealant on the splines of the shaft and sprocket as a "back-up" to the O-ring. As this would have no negative affect that comes to mind, I don't see any reason why you can't if you choose to, but it's probably a waste of time.

    The only thing left to do is install a new or used nut or bolt. New bolt kits (bolt and cup washer) have a pre-applied locking agent on the threads...nice. In the '03 manual, KTM recommends using loctite 243 on a used bolt, and a torque value of 44 ft.lbs.

    3-27-06 Addendum: The sprocket bolt has a shoulder or "step" on it that measures about .080", while the washer which fits over the shoulder, measures about .060" thick(all I have are used parts, so these numbers may vary).
    The washer is dished, so when torqued the washer compresses, tries to flatten out... but as there is no real clamp load on it other than the tension applied by the dished shape being compressed... it tends to rotate a bit.

    This by the way is what holds your sprocket laterally on the shaft, so if the washer gets flattens out and gets loose, you will have some lateral sprocket play. You may also have a leak, as the pressure which normally holds the sprocket spacer firm against the inner o-ring will be non-existant.


    3-27-06 Addendum: The maximum allowable axial (lateral) endplay for the transmission shaft is 0.40mm (.016"). Something to check on high mileage bikes.

    A dab of paint or three to keep an eye on things... and we're all done.

    [​IMG]

    That's it... hope it helps somebody somewhere.

    Chris

    To print a copy of this guide, go to the top of the page and click on "Thread Tools" then click on "Show Printable Version"
    #1
  2. G.Kennedy

    G.Kennedy ...

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    As usual ... excellent job on the write up ... thanks Creep. How many miles on your 640 ???? for seal longevity reference.
    #2
  3. Loadedagain

    Loadedagain making chips

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    thought you wasn't gonna be paint markin that washer anymore?
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  4. creeper

    creeper Still alive...

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    Thanks G. A bit over 9K miles. If I were to estimate, probably over 60% of that mileage is on the street. Another way to look at it... probably over 60% of total hours has been in the <S>mud</S>... dirt. So time in the dirt might have more of a impact than mileage.

    C
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  5. creeper

    creeper Still alive...

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    Yeah... I guess it's a useless habit. :D

    At least painting the bolt and sprocket makes sense.
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  6. rapiti

    rapiti IOR Veteran

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    Aw, c'mon! The warm color sets off the final pic, and it looks sooo professional. :D

    Thanks again, Chris. I have had the seal for months, but lack the o-ring and/or a new spacer. 7350 miles on my bike, but as mentioned elsewhere, I'm pretty sure I buggered it by fitting the chain a link short. Live & learn...

    Oh yeah, one more question. What is a fair expectation of cam bearing failure? I have heard 10k miles. What is the cost to pre-emptively replace these, and are the replacement parts expected to live longer, or just a 10k thing? Is it the small needle bearing that is failure prone?

    Could be the next DIY project. :ear
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  7. creeper

    creeper Still alive...

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    I would imagine, but can't confirm, that a too tight chain adjustment might have more to do with how long that seal lives than any other factor.

    Ya' know... I haven't seen or heard any continuity when it comes to cam bearings. Sure, there have been people that have smoked theirs at low mileage... but is that common, or is it just one of those "shit floats" internet phenomena’s?
    One or two or even three guys on the internet who throw a hiss about early cam bearing failure doesn't mean an epidemic... just means they all have computers and internet access. :evil

    We've all heard of others who go 40K miles with nothing more than oil changes... so I got nothing for you at all when it comes to cam bearings.

    I suspect that for every guy that has one fail early (and why did it fail, you might ask)... there are 20 guys who've never had a problem.

    Ciao,
    C
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  8. Ian640

    Ian640 Been here awhile

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    Thanks for the write up creeper :thumb.

    This seal failed on my 02 640LC4-E at around 13000 miles. I wasn't in a position to change it myself at the time (I was travelling so a dealer did the fix) but the write up will come in handy next time.

    After the trip, at around 15000 miles I gave the bike an overhaul, and discovered a number of other items needed replacing:

    1. The small needle roller camshaft bearing was slightly 'notchy'. I replaced it. The larger camshaft bearing was fine, but I bought a replacement anyway. Incidentally, the original large camshaft bearing was a sealed bearing, the replacement bearing (KTM part) not.

    2. The bearing that supports the rear wheel sprocket carrier was also notchy.

    3. The lower rear suspension linkage bush that supports the shock had failed.

    4. The water pump seal on my old 640 Adventure also failed at around 15000 miles. So I'm rebuilding the water pump on the E in the next few weeks (current mileage on the E around 15500).

    5. Also in the next few weeks I'll be replacing the cam follower bearings. Perhaps over-cautious.

    Usage? The bike's not had the easiest life: travel, commuting, competition, trails.

    Cheers.
    #8
  9. G.Kennedy

    G.Kennedy ...

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    I am at about 15,500 and every thing on Ians list has been bouncing around my brain as things I need to check.

    I picked 20k as a nice round # to do a big teardown and check all the major bearings.
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  10. creeper

    creeper Still alive...

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    When it reaches a point where I have to fix/replace something every few months, that's when I'll take it down to the crank and go thru all of it.

    Then again... the LC4s replacement is due in a year or two. :evil ... and who knows who and what else will come out if the trend towards do-all bikes continues to escalate.

    I love my KTM... but I ain't married to it. That and I ain't gettin' any younger either, so my needs may change.

    I do have this... "Vision" I suppose, where I keep the KTM for 20 years (Ha! like I'll live to see 70 :lol3 ) and just keep riding and rebuilding until it's a classic. 'Course, I'll have to convert it to bio-diesel at some point. :D
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  11. Ian640

    Ian640 Been here awhile

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    When I bought the E i had some idea that when I parted it with it, it'd be because it was in my testament. It's given me some adventures and I don't mind fixing it up. It's nice to have a rosy vision of some old classic lying in the back of the garage.

    Then I realise that it's just a lump of metal/plastic/rubber, and may well be well and truly obsolete when the world's oil supply runs out.

    By the way any further news on a replacement for the LC4? Will there be an F650 based HP1 from BMW? Seen a couple of HP2s recently, a bike that's tempted me because I'd guess it would be a little for comfortable than the LC4-E on the highway due to the two cylinders - I'm not getting any younger either.
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  12. creeper

    creeper Still alive...

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    Nothing you could call concrete information. Informed conjecture salted with the usual rampant, wildass daydreamin'... in other words, nothin'.
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  13. Nom de Guerre

    Nom de Guerre Long timer

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    Sweet write up with excellent pics to accompany it. Nice job, creeper! If and when I need to do it, I'll know where to read up.

    The only thing I saw that you might want to correct is a typo on your 2nd to last sentence:

    Meat, add it to the index if you haven't already!
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  14. creeper

    creeper Still alive...

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    One typo?... that's all? Have you taken over for ChrisC as the spell check police?

    :D

    OK... I'll fix it, God forbid I have a single letter out of place. :ksteve
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  15. Nom de Guerre

    Nom de Guerre Long timer

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    Ya know... it's just one of those things. I notice typos, and I am plagued by making them all the time. That's why so many frigging posts of mine are edited. It annoys me that I make 'em. It doesn't really bother me when others do, but I think I assume it must bother others since it bugs me. :dunno :lol3
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  16. creeper

    creeper Still alive...

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    You even got an editorial byline...

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  17. Nom de Guerre

    Nom de Guerre Long timer

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    I'm not biting on "bastadge." Intentional misspellings don't count. :lol3
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  18. meat popsicle

    meat popsicle Ignostic

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    What- this? Is this another one of those "How-Tos"? :evil
    Creeper: good job on this, very informative. Can't wait until I have to do this too... :lol3
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  19. meat popsicle

    meat popsicle Ignostic

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  20. ChrisC

    ChrisC Amal sex?

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    Hay, feck all uze guize an da hurse ya road in on........ :eek1
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