KTM 640 - engine randomly dies

Discussion in 'Thumpers' started by Queen of Spades, Dec 4, 2012.

  1. Queen of Spades

    Queen of Spades tall drink of water

    Joined:
    Mar 20, 2009
    Oddometer:
    1,003
    Location:
    Decatur, GA
    Started a couple weeks ago on the way home. The bike was properly warmed up and out of nowhere - died at a traffic light. A couple presses of the Magic Button and she fired up and drove home the rest of the way.

    Yesterday I went for a play ride and the bike again stalled just as I was getting onto 285. Like before a couple stabs at the MB got things going again. The bike ran fine the rest of the afternoon - logged about 40 miles, 10 of that woods trails including a couple creek crossings. Not a whimper.

    Obligatory trail pic:
    [​IMG]

    This morning on my way in to work, the bike stalled again after coming to a stop sign. This time it was a little harder to get going. A couple minutes later it finally lit up, and I rode the rest of the way to the office without a problem.

    Tonight, again at a red light, the bike inexplicably died. I pushed to the side of the road and continued trying to get it to light up - nothing doing. I had no tools so I couldn't do any troubleshooting. I paged a taxi and after going home to get my pickup, the bike started right up.

    Loaded it up and when I got home, I unloaded and again started it up - it ran fine for about 30 seconds, then died. Wouldn't start again.

    WTF is going on?
    #1
  2. AustinJake

    AustinJake TE450-KLE-FXDWG

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    I had the same problem on my Husky, intermittent dying and restarting, also some cutting out before dying. Turned out to be a rubbed raw wire, and this wire just happened to be connected to the fuel pump, the fuel injector AND the coil!

    [​IMG]
    #2
  3. bmwktmbill

    bmwktmbill Traveler

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    I would check the ground connection at the battery for tightness, then the positive connection.
    Wiggle the main fuse, make sure the contacts are tight.

    Do you have issues with the dash lights?
    If you do I would consider the ignition switch, not a bad idea to unplug/plug that connection to the main wiring loom.

    Do you have a kickstand switch?

    bill
    #3
  4. Steveman

    Steveman Been here awhile

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    Oddometer:
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    First two things to check before you look for problems with wires and/or terminals is:

    a) does she get fuel
    b) do you have a powerful spark

    You have exactly three possibilities, no/not enough fuel (a), no/not good enough spark (b) or both (a+b).

    As soon as you have found out if it is a fuel or electrical problem (no spark) you can go and look for the cause.

    Good luck
    Steve
    #4
  5. Queen of Spades

    Queen of Spades tall drink of water

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    Last winter I lost all electrical and eventually traced it back to a connector with two wires that looked scored/burned. A few weeks ago I had some trouble with the headlight failing due to a loose fuse connection.

    I wouldn't be surprised if something else is wonky with the wiring.
    #5
  6. Betelgeuse

    Betelgeuse Don't Panic

    Joined:
    Apr 7, 2005
    Oddometer:
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    Location:
    Central NH
    X2 from bmwktmbill. Check the wiring under the ignition switch by wiggling the loom leading up to the switch itself. I've had a wire break off up there twice. You can't see if it's broken unless you take it off and look for it.
    Good luck.
    #6
  7. Grreatdog

    Grreatdog Long timer

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    Location:
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    Anytime a bike acts like that the first thing I do is ride around with the gas cap loose to see if it is a venting issue.
    #7
  8. motomark39

    motomark39 I reckon so

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    Location:
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    I have had two ignition swithches go bad on two different 640s
    #8
  9. clintnz

    clintnz Trans-Global Chook Chaser

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    If all the wires behind the dash & the sidestand switch check out ok also have a look at the wires coming out of the igniter box under the RH sidecover. I had some of these rub through against each other which caused some intermittent cutting out. It was hard to see anything was wrong until the wires were moved & inspected closely.

    Cheers
    Clint
    #9
  10. MORT666

    MORT666 Been here awhile

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    Change the plug cap.:norton
    #10
  11. Queen of Spades

    Queen of Spades tall drink of water

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    Ya'll assign too much homework!!! :freaky
    #11
  12. bmwktmbill

    bmwktmbill Traveler

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    How right...change the plug too.
    bill
    #12
  13. biensur22

    biensur22 Been here awhile

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    San Diego, CA
    This was happening on my 620 adventure too. After popping the plug and discovering I had no spark, I pulled the whole fairing and electrical compoents from the front end to limit the variables. Bike fired right up and idled smoothly. Took the fairing.electronics on the bench and discovered various frayed powered wires. I cleaned them up and plugged everything back in. Haven't had any problems yet.

    So here's the break down:

    1. Check that you have consistent spark (pull plug, attach cap, ground it against the frame, hit the starter - should see a blue spark)

    If no spark, check your electrical as discussed. If you have spark:

    2. Check fuel supply. Make sure your starter and idle jets are clean/clear, and check your float height. Clean/replace fuel lines, filter, etc.
    #13
  14. SRG

    SRG SRG

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    There is a vacuum line that runs from the fuel pump to the carb. If it gets kinked the bike will die.

    May not be your problem, but it's easy to check.
    #14
  15. Queen of Spades

    Queen of Spades tall drink of water

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    Update -- finally ventured out into the cold, cold shop to peel off the pumpkin's seat & plastic. Upon removing the seat I saw two red/yellow wires dangling as though they may have been connected together.. on closer inspection it looks like they were plugged into a white connector, and worked loose. A few inches away from the now loose end, there is a fuse holder (fuse OK).

    I can't find the exact yellow/red wire in my diagram, though. Did KTM ever publish a color wiring diagram for the LC4 640 models? I cannot find a fuse holder with yellow/red wire on my diagram.
    #15
  16. Queen of Spades

    Queen of Spades tall drink of water

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    I'll snap a pic and upload in a bit.
    #16
  17. Queen of Spades

    Queen of Spades tall drink of water

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    [​IMG]


    [​IMG]
    #17
  18. Laromonster

    Laromonster Vesperado !

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    You lost yer battery..:D
    #18
  19. Queen of Spades

    Queen of Spades tall drink of water

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    #19
  20. Queen of Spades

    Queen of Spades tall drink of water

    Joined:
    Mar 20, 2009
    Oddometer:
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    Location:
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    Returning to the topic at hand, does anyone have a picture of this section of wiring on their 640 LC4? Mine is a 99 model (enduro).

    I'm unsure if both of the ends of the yellow/red wire are to be joined and inserted into the white plastic coupling (see the empty brass fitting).
    #20