KTM LC4 (640) Thread Index

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

  1. hillbilly enduro

    hillbilly enduro Adventurer

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    Oddometer:
    25
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    I should probably explain better... I didn't intend to re use the old rollers, when failure occurs. I'd buy a new set/s and then just reinstall with a hardened pin instead of the KTM pin. I'm aware that the KTM pins are also hardened. But as it seems that it's always the pins and not eg. the rollers that's wearing out, then maybe the pins should have been harder.

    Hope this makes sense...

    Comparison with bicycle bearings is kind of useless, as those races is just a piece of pressed sheet metal, and not hardened...

    But your comparing to steering head bearings maybe is correct, since the load on the rocker rollers isn't constant either...
  2. gunnerbuck

    gunnerbuck Island Hopper

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    The KTM roller axle pins seem to be quite soft, so installing a harder unit may work to extend the life somewhat...

    Replacing the roller at every 25,000 miles is not that big of issue for me as I usually have the rocker cover off at that mileage anyways to rebuild the waterpump...
  3. Mo-Tarded

    Mo-Tarded Been here awhile

    Joined:
    Jun 25, 2008
    Oddometer:
    191
    Location:
    Show Low, AZ, USA
    Katrina has developed a leak when the gas is "On". Also have a slight hesitation mid-range (feels like a fuel starvation). So I'm going in... (Again).

    I do not see this screen (referenced above) anywhere... ...but I'm part blind so may not know where I am looking.

    Does someone have a better exploded view of the BeaST carburetor than the one below ?

    http://www.motorcyclecarbs.com/Mikuni_BST_Carburetor_C685.cfm

    Thanks in advance... - Robert
  4. Young-Gun

    Young-Gun KTM Tragic

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    Dec 6, 2005
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    [​IMG]

  5. Mo-Tarded

    Mo-Tarded Been here awhile

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    Jun 25, 2008
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    191
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    YG-640 Yes ! Alot ! ...however I still do not see a screen/filter on the gas intake. :D

    I guess I'll go in eyes-wide-open. I'll check the tank filter in the process as well.

    Fun fun fun... Thanks !
  6. clintnz

    clintnz Trans-Global Chook Chaser

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    It is tiny. The bent steel tube that comes out of the carb where the fuel line enters from the tank, in the end there is a semi conical plastic insert, lever that out carefully with something sharpish. With the carb out you can just look down the tube & see if you can see any crud.

    Cheers
    Clint
  7. bmwktmbill

    bmwktmbill Traveler

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    Jul 16, 2005
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    This analysis makes sense. A solid chromed pin and chromed sleeve in the roller would work, it could be drilled length ways with a couple of oil holes to the surface to increase internal lube.

    The contact area would increase, the pin size could be maximized larger.

    I'm not sure why KTM chose the system they did, perhaps valve overlap was a problem plus spring strength?, the whole engine is designed to rev quick and it does.

    I watched a KTM factory mechanic work on my motorcycle at the factory.
    The way he threw stuff away had me dumpster diving while he inhaled a liter of beer with lunch.
    IMHO.
    bill
  8. gunnerbuck

    gunnerbuck Island Hopper

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    KTM must like the follower roller design as they used the same system in the 690 but used shims on it rather than the bolt and lock nut for adjustment... Also they do not offer only the rollers for the 690, you have to buy the whole rocker arm assembly {$$$} when replacement time comes...
  9. HydroDog

    HydroDog Been here awhile

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    Dec 20, 2006
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    Mossyrock, Wa
    I know back when I had my 01 Husaberg there was talk about the lack of cam roller longetivity do to reduced valve lash clearance in between valve adjustments. Reduced clearance equals more roll time. The other reason was poor heat treatment quality between batches of roller pins. Probably both bogus ideas.
  10. hillbilly enduro

    hillbilly enduro Adventurer

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    Jun 20, 2012
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    That's what I was thinking. I know It might not be a big issue changing them. But if you only had to change them every other time, then you'd save 100$ = more money for gas or other needed parts. :clap

    But still I hesitate a bit, as I'm afraid it would make things worse instead of better:puke1
  11. mgorman

    mgorman Crashing since 1964

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    On the average Huffy or cheap bicycle yes, but take apart a Campagnolo or good Shimano wheel hub and you will see a huge difference in quality, night and day different.
  12. bmwktmbill

    bmwktmbill Traveler

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    The hell of it is you never know when it will happen. I had one start to go at 15K miles. I felt lucky to find it.
    bill
  13. stumpy-ktm

    stumpy-ktm Adventurer

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    Jul 31, 2012
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    kapiti coast New Zealand
    ok here is some pics of the part you are looking for



    [​IMG]
    [​IMG]
    [​IMG]
  14. hillbilly enduro

    hillbilly enduro Adventurer

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    Jun 20, 2012
    Oddometer:
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    Ok. Then I learned something again today :clap I still prefer the ballbearings over the conical ones though...

    Yes it's not good. It's about the same story with my 625. PO replaced both intake roller and cam just before I bought it. It was at about 16500 km. But it had been stolen and probably been ridden like so, that can't help either.
    Unfortunately he replaced the roller with a good used one :cry, so I'm going to replace both rollers in near future, before it costs another cam:puke1
  15. Mo-Tarded

    Mo-Tarded Been here awhile

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    Clint/Stumpy: I FOUND IT ! I took it out completely... I'm going to put an inline filter in. Something visual that I can see crud in. Thanks guys !

    Zen my ass... * cursing * ....but I'd strangle ( as to offset the period of time I spent cussing trying to reinstall the choke cable into the BST) the idiot that built a plastic choke cable retainer in the stupid carburetor ! ...and only THEN did I recall reading that there is an aluminum one available.

    So my NEXT question is: Is the replacement part aluminum ? ....or is it an aftermarket gizmo ?

    Thanks again in advance for any help !
  16. bmwktmbill

    bmwktmbill Traveler

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    My choke fitting ran broken for quite a while.I upped the slack a little.
    bill
  17. dnrobertson

    dnrobertson Big Bike, Slow Rider

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    Jun 30, 2008
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    983
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    This may be worth a look.

    I have swapped to an FCR carb, and the standard Mikuni plastic choke retainer fits in the FCR. I have looked at the hot start mechanism on the FCR and the retainer for that looks the same as the choke. There are replacement aluminium retainers availble for the hot start.
  18. biensur22

    biensur22 litigious poster

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    Oct 26, 2011
    Oddometer:
    183
    Location:
    Denver, CO
    This might strike some as an odd question but I've looked throughout and can't find an answer. I'm trying to install a center stand on my 98 620 adv but I'm struggling to figure it out. It seems that one mounting hole (l/h side) is threaded while the other is not. Thus, when I fit it into place the post on the right side of the center stand slides in properly, but the left has the same side threads as its hole, therefore it needs to be spun on. What's going on here? The bottom hole is the one on the left side that I'm using. The kick stand is still on tho I know it will need to be removed to use the center stand, but do I need to take it ff for installation? What am I missing?[​IMG]
  19. Dolly Sod

    Dolly Sod I want to do right, but not right now

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    Gotta take the KTM side stand off to install the center stand. The center stand fits into the very bottom holes on the frame, almost like stamped steel down there. It does not thread in, I think the threads you are seeing are from the side stand bracket.

    I've been thinking about this...

    [​IMG]

    ...as I have both the KTM side stand and center stand. The center stand alone is a pain IMHO, but I like the idea for working on the bike and flats.

    Might end up getting a SW Motech jobbie, but have trouble with the $120 price tag.
  20. biensur22

    biensur22 litigious poster

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    I see what you're saying, but my frame hole is definitely threaded. I wonder if I should just drill it out.

    I like the idea of both, an I would generally prefer the kick over the center for convenience, but the stock kickstand is so flimsy I'm always affraid it's about to break off.