Yet another LC4 electrical/starting thread

Discussion in 'Thumpers' started by DolphinJohn, Nov 9, 2012.

  1. Donkey Hotey

    Donkey Hotey De Jo Momma

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    It's either the starter motor or one of the three cables.

    If you want to really be doubly sure, disconnect one of the cables at the relay and touch it to the remaining one. If the engine doesn't crank, you've eliminated everything else on the bike. That's the simplest circuit: battery straight to the starter. The whole rest of the bike could be missing but, that should spin the starter.

    You said you disassembled the starter and verified it was good. How did you verify? Did you check each set of windings with an ohmmeter or just get it to spin on the bench when connected to a battery?

    You may have one or more shorted or open windings in the motor and once it spins to those, it will stop.
    #21
  2. DolphinJohn

    DolphinJohn Caveman

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    I said before the starter turns the engine over and even starts the bike just fine when powered from jumper cables directly to the starter. When I opened it I rebuilt it with a rebuild kit, even though everything looked like new in there.

    I also replaced the cable from the relay to the starter. I will try the battery straight to starter method.

    I ordered both relays yesterday.

    .

    .
    #22
  3. Donkey Hotey

    Donkey Hotey De Jo Momma

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    So what happens if you use a jumper cable from the battery straight to the starter terminal (now, in the bike)?
    #23
  4. bmwktmbill

    bmwktmbill Traveler

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    http://www.apriliaforum.com/forums/...e-won-t-start-Relay-and-battery-are-ok-though

    or...

    Quote...
    The starter solenoid is integral to the starter, which is located below the intake manifold and requires a fair amount of disassembly for access.

    The start relay (and all relays) consist of a control circuit where a relatively small amount of current (typically less than 200 milli-amps) flows through a fine wire coil around an iron core creating a magnetic field. The magnetic field pulls a thin metal strip towards the magnet, closing circuit contact points through which flows the large amount of output current that the particular relay controls.

    When the start relay "buzzes" the thin metal contact strip is not being firmly held in place to the stationary contact by the magnetic field, and the two contact points through which the output current is supposed to flow vibrate against one another - creating noise, an inability for the correct amount of output current to flow (ie: the starter doesn't engage) and electrical arcing (with resultant burning and ultimate damage) between the two contacts.

    The real question arises as to why, specifically, the relay contacts are not making fast and secure contact with one another when the relay is energized.

    Insufficient current flow through the control coil of the relay will result in a weak magnetic field being genererated. Current flow is directly proportional to available voltage, and inversely proportional to resistance.

    The diagnostic of the issue, with resulting "solution" would be to capture electrical data of the event while it is occurring and measuring voltage drops accross various components of the circuit, which would be the ignition switch, related wiring and the relay itself.

    Simple concept, and relatively easy diagnosis - provide the diagnostic tests are being performed correctly while the fault is actually present.

    Short of proper diagnosis, it's all pure guess-work and speculation.

    John,
    Disconnect the switched wire to the starter relay and jump the relay with a jumper wire off the battery. I think the switched wire will come from the Aux relay. It should be hot when the starter button is pushed.
    The BR color for KTM is usually a ground (-) wire and should show no voltage.

    What happens when you jump it, does the starter turn?

    Check you connections and plugs especially the neutral switch, clutch switch, key switch. Plug, unplug, clean.

    If the nertral switch or clutch switch is bad or the starter button is making poor contact, relays won't help you.

    IMHO.
    bill
    #24
  5. DolphinJohn

    DolphinJohn Caveman

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    The saga continues..... but there are clues :lol3

    I replaced both starter relays and nothing changed. I started looking real close at some of the wiring and plugs near the battery and relay.

    KTM uses some really thin wires. A couple years ago I had an electrical issue and finally found it was a broken wire, the small one coming out of the fuse on the positive cable at the battery. In the process, before I figured out it was the wire, I replaced the voltage regulator. So, I've got some nice new wiring in the area and some old worn wiring.

    So today as I was moving some wires around and hitting the starter button, it kicked the starter just for a second. Ahah!!

    So looking at the wires and plugs that I was touching, they are in bad shape: exposed wire at the connector, and very stiff, brittle wire on those. I tried cleaning all the plugs and moving the wires around while trying the button but could not recreate the starter turning.

    I need to replace some of the wires and I think it should be good. My friend is going to help me, he's got a soldering iron and is experienced with this stuff.

    I'll report back when I know more.

    Thanks for all the help.

    .
    #25