KTM LC4 (640) Thread Index

Discussion in 'Thumpers' started by meat popsicle, Jul 9, 2005.

  1. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    Sumi- I'll post up a link to the Loctite thread, but be warned, If you choose the wrong type of RTV the valve cover will leak. Additionally one of the by-products the acetoxy gas features is it's corrosivity to electrical components and ferrous metals.

    RTV's which smell like vinegar do not withstand exposure to fuels, oils, ethylene glycols, etc. These are called acetoxy-cure or acetic acid cure RTV's. An example of this is most all types of cheap RTV. Red "High-Temp" RTV's such as Dow Corning 736 is also a corrosive RTV.

    All RTV's are not created equal.

    Don't use any vinegar-smelling RTV to seal up that valve inspection cover.

    The debate has gone on for years as to what to use, but here's what I've done and my inspection covers don't leak a drop.

    Remove each cover and make note of the raised metal bead in the center of the mating surface.

    Sand the tiny ridge off by placing a sheet of fine grit sand paper lubricated by WD-40 or the like on a flat surface and work the inspection covers around on the sand paper until the ridge had been removed.

    Clean both covers, place a thin bead of any of the Loctite Gasket Eliminators on the freshly lapped inspection covers and reinstal them.

    You'll never have another leak.

    If you think about it, by sanding off the ridge and NOT using archane cut gaskets we're dramatically increasing the amount of mating surface for the application. And off of the KTM assembly floor, the mating surface is pencil thin. The cut gasket takes a compression set and relaxes and a leak rears it's ugly head.

    Here's a thread to read over if you like:

    http://advrider.com/forums/showthread.php?t=265016

    Dirty
  2. Sumi

    Sumi Long timer

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    Thanks, If everything else fails (old gasket, new gasket), I'll give this is a shot!
  3. rz35027

    rz35027 Been here awhile

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    Nice...
  4. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    Thanks, this is what I do for a living.

    Such is the life of a Loctite guy.

    Dirty
  5. bmwktmbill

    bmwktmbill Traveler

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    Dirty,
    Last I sealed the top of the engine I used Red hi-temp RTV.

    It worked OK, leaked a little.

    What are you recommending for that these days?

    Also on the road it might be necessary to reuse a base or head gasket if the engine has to come apart and fresh spares aren't available.

    Can you recommend anything for reuseing these and if so does the torque spec stay the same?

    Should the head be retorqued?
    Should the engine top?

    bill
  6. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    Bill-

    The automobile industry stopped using cut gaskets like the ones used to help seal the valve inspection covers on the LC4 Mill back in the '70s. And there's a reason for it.....cut gaskets are prone to taking on a compression set which results in leaks.

    I try not to use cut gaskets on anything that uses a spark plug in our house and use instead...you might guess, one of which ever Gasket Eliminator product I have closest. 518, 515, or even 510 all would be entirely suitable.

    Acetoxy cure RTV's like ALL red high temp RTV's don't play well with non-polar fluids such as oils and fuels. The hydrocarbons absorb into and are attracted to the silicone molecules, then sometimes slowly and sometimes rather quickly the RTV breaks down and a leak is born. This is what you experienced. Then there's the small bit of squeezeout that will become dislodged and might come to rest at an oil pump intake location.

    Plus RTV's we all use are cured by moisture. As soon as a thick or thin bead of RTV or any other solvent based gasketing product is applied it immediately begins to cure and skin over. If you fiddle around once you draw out a bead of RTV, by the time you mate the surfaces it's already skinned over to the point the exposed product has cured to the point it won't wet out the mating surface which is needed for a satisfactory seal.

    Gasket Eliminators have no open time to worry about like you do with the gasketing products mentioned above. You could apply the material, go to lunch, take a week vacation, then return and mate your parts. It doesn't begin to cure until you remove air from the equation...mate your parts and tighten things up.

    A little 6ml tube (think small like a tube of Chapstik) of 518 is an ideal thing to have in a tool bag.

    The use of Gasket Eliminator does not change the torque specs.

    On the inspection covers I dab a thinnish visable film on the top of the head, place the covers in place, then with a bit of blue threadlocker on the hex head bolts thread them in. Once finer tight, I'll go back around and snug everything up, then wipe off any squeezeout to keep the dust from finding a place to call home. Because we're not using an elastic/mildly compressible gasket, arriving at "tight" feels different. I suspect you work on your own bike so you should know how tight...tight is. I've never torqued these buggers with a real live clicker torque wrench.

    A head or base gasket can be removed and reused by dressing both sides of the gasket with a thin film.

    Careful work with a razor blade will allow you to remove the head or base gasket. Tedius, but I've done it with no real issues.

    Once everything is buttoned up, no need to re-torque simply because you upset the seal. Same goes for nuts and bolts with a threadlocker.

    My LC4 does not have any sort of oil leak.

    Dirty
  7. bmwktmbill

    bmwktmbill Traveler

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  8. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    Yep, only I vote for 518 more than 515 simply because it fixtures (holds your parts together) a bit more quickly than 515.

    Instead of an Amazon-type place, I suggest going to one of your local Industrial Distribution/Bearing/Power Train houses like Motion Industries, Applied Industrial Technologies, Grainger, Fastenal. If they don't have the stuff, you'll get it the following day.

    Some part numbers:

    pn. 51817 Loctite 518 Gasket Eliminator, 6ml "Travel Size"
    pn. 51831 Loctite 518 Gasket Eliminator, 50ml

    Dirty
  9. SCsurfer

    SCsurfer surfing explorer

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    Hey Bill , I used Honda Bond when my rocker cover started leaking at 8k miles . Now at 14k and still no leaks .
  10. bmwktmbill

    bmwktmbill Traveler

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    I have used Honda bond myself several times and it works but...it's a PIA to work with and a PIA to clean off when the time comes to open the chest.

    That said I carried it RTW on one trip. It started to harden up after a couple of years. I will try the Loctite products next.

    They sound like the final solution and will multi-task.
    bill
  11. flashover604

    flashover604 tailgunner

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    Hóla, Seńor Sanchez. Any guess as to what the grayish white toothpaste looking stuff is sandwiched between the head and leaking rocker cover of your old, my new 640? It was up posed to have had the top end rebuilt 1000 miles before I got. Hard to tell what the shop used, but it's fugly. It'll be cleaned off and replaced by 515 or 518 when I get around to it.... Still a great bike, btw. It almost got it's first whitetail last week...

    http://[​IMG]

    Shown with a buddies Trail 90. I think I can get IT for $500. I'll just throw it on the back for a spare....
  12. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    Flashover- I was about to say what happened! It shrunk and has fork boots now-then I noticed the Grey Mare.

    The guys last into the engine likely used Hondabond/Yamabond, XXXXXbond, that clay/solventbased sticky, pain in the arse to clean up stuff.

    Patience, time, and a non-marring scraper to get it off are all your friends.

    Dirty
  13. flashover604

    flashover604 tailgunner

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    Grey Mare. I like it. That little trail 90 will run 41 mph all day long. It won't do 42. As for the MysteryBond stuff, it looks like it was put on with a paint brush. This bike is a ball. I used the spare switch on the dash for my clutch/neutral switch for the time being. Now I can bypass it when I want to. I may go back and run the wiring from the clutch through the switch so I can have the original function, plus a complete bypass. Right now it's all or nothing.
  14. racedawg

    racedawg Have bike will travel

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  15. dirty_sanchez

    dirty_sanchez Dirty_Sanchez

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    So with the spare dash switch thrown you can now start it while in gear....with the clutch lever pulled in?

    Anyone else know if we can start the bike while in gear/clutch lever pulled in by disconnecting the wire down down near the oil filter cover and counter sprocket?

    Dirty
  16. flashover604

    flashover604 tailgunner

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    When I got it, the connector was hanging at the perch, so it would only start in neutral, whether the clutch was pulled in or not. Now, with the switch off, it'll still only start in neutral. With the switch on, it'll start in gear or neutral, with the clutch lever in or out.
  17. juames

    juames Have Fun, Don't Die!

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    What's wrong with this picture?

    Picked up a 2002 640 Adventure about a month ago and I'm loving it!

    Needs a bit of jetting, but other than that its in great shape! Shouldn't there be a snorkel on top of the airbox? How would this affect the way the bike runs? It idles a bit rough, and I get some surging at low rpms between 0-1/4 throttle.

    [​IMG]
  18. bmwktmbill

    bmwktmbill Traveler

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    What carb?

    If it's the BST 40 try raising the needle a notch.

    The bike will run fine with stock jets.

    What jets do you have in there?

    Clean the carb.
    bill
  19. juames

    juames Have Fun, Don't Die!

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    OEM carb...not sure of the jets. Haven't had the carb open yet. Stock exhaust.

    What affect if any would removing the top of the airbox have? Looks like it was cut off.
  20. gunnerbuck

    gunnerbuck Island Hopper

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    Removing the top of the airbox will add more air to the mix so you can run bigger jets and in theory gain a bit of horsepower... In order to take advantage of this your exhaust has likely been cored out to allow the extra volume of combustion to exit the engine...

    On the downside: your filter will need more frequent cleaning... The way the top was butchered of your airbox you are losing the integrity of one of the most watertight airbox designs...