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getting spark to plug only by turning stop/run switch!

Discussion in 'The Garage' started by Whatevertskc, Apr 17, 2011.

  1. Whatevertskc

    Whatevertskc XS400 New Member

    Hello Everyone, My problem is when I turn the key on with the run switch on off everything seems ok, as soon as I turn it to run I get a spark even without pulling in the clutch lever, if this happens with spark plug wires hooked onto the plugs,would that not start the engine even without touching the starter button. This don't seem right.
  2. bcware

    bcware Well-read Top Contributor

    Getting a spark alone won't start the engine; it needs to turn and create compression to run.

    What is the history of the bike and any maintenance and modifications? I would look at the points and the wires connected to the points. Everything under the points cover is designed so that a circuit is completed when the points touch at a specified time. If, for example, the insulating washers used to attach the points wires were not insulating (i.e. allowing the points wire to make contact with any metal part) then you'll get a spark when power is applied regardless of timing.
  3. drewpy

    drewpy Excess twin Top Contributor

    had to read the text 4 times, and still didn't get what your saying!

    looking at the title, you only get a spark by turning the on/off run switch?

    I think BC has the answer, your basically using the run switch as a contact by turning it on and off!

    BTW its usually polite if you give an introduction first :wink2:
  4. jayel

    jayel #9 Guru 78 SR500 80 XS11

    just like a set of points, making and breaking, flipping the switch creates and collapses a electrical field in the coil = spark at the plug
  5. lhaolpa

    lhaolpa XS400 Junkie

    You need to remove the keyed ignition switch,take it apart and clean it. Same for the kill switch,take it apart and spray it with contact cleaner or WD-40.This happened to me on my Dt400,I didn't have spark,and I replaced the coil,no spark so I started checking for a short.Found switch had 6v in 0v out,took it apart,cleaned the contacts,put di-electric grease on it and VOILA it works. lha
  6. Once had my air cooled VW start when I turned the ignition switch to the "on" position. Everything was just right in the cycle for the coil to fire a plug in one cylinder and ignite the gas mix. BTW, the engine had just been shut down a few minutes before. That was a strange feeling!
  7. pcream

    pcream XS400 Enthusiast

    Sorry to revive a long dead thread, but I am having nearly the exact same issue with my DOHC 1982 XS400 Seca. I road in the morning, the day after my bike had been in the rain, to work with no issue. When I was about to head home, I tried to start it and it turned over fine but wouldn't go/catch at all, just endlessly turn over. Figured out there was no spark while it was cranking on either side, but curiously I would get a big spark when I put the killswitch to off while the key is on. So much so that while cranking and then quickly hitting the kill switch would cause the pistons to briefly fire. Also, weirdly the turn signals don't flash anymore as they normally do, they just remain solidly on when switched. No idea what that is about.

    I tried several things, cleaning the ignition switch, charging the battery to full, new spark plugs, etc. Nothing seems to fix it, I would suspect the TCI, but I had replaced that a few months ago when I was having problems with only one side firing. Based on this thread, I am now assuming there is a short somewhere in the wiring, because of the bike being in the rain the day before and perhaps corroding something. Is it possible the ignition circuit is crossed with the turn signal circuits? I think the relays are working correctly because they make a loud clicking noise when the key is turned to on and the kill switch is turned to on.

    Does anyone have any ideas, was there any resolution to this problem? Should I try to clean the key switch as well? Continue testing for shorts? I'm a little lost here, as all of the components appear to work, the spark is strong enough to fire the cylinder but it just doesn't go at all while cranking and only when the kill switch is turned to off.
  8. Gra900

    Gra900 XS400 Enthusiast

    Hi Guys, there a bit of a coincidence between this post and the one above
    DOHC Pulsar coil rebuild
    Same symptoms
  9. pcream

    pcream XS400 Enthusiast

    Indeed, this post and the Pulsar coil rebuild both appear suspiciously familiar to me. Hopefully these are some hints as to what is going wrong, it's going to require a lot of electrical troubleshooting to figure it out.
  10. pcream

    pcream XS400 Enthusiast

    I apologize for the delay, but I finally got around to starting to troubleshoot over the weekend with the good weather that we had. Ran through the ignition checklist n the manual: check connectors -> battery voltage -> fuze continuity -> coil resistance -> pick up coil resistance and everything was reading correctly. Decided to try to start it and bam it started up immediately. Whatever was wrong had fixed itself. I'm now almost certain there was a short that finally dried up with the 60F weather we had over the weekend. I'm going to go over everything with some contact cleaner, but based on the symptoms I think there was something shorting between TCI and the coils, so I'm going to give those a good clean.

    If I find something during the cleaning, I'll post it here so these threads can have a final resolution to the problem.
  11. pcream

    pcream XS400 Enthusiast

    Ok, update. So the problem would appear/disappear seemingly at random, I was starting to lose my mind. Finally, looking at the circuit diagram I saw that the neutral cutoff relay was in the ignition circuit and decided to test it by bridging the red/white wires that are connected when the neutral gear switch is engaged. Fired right up! Pretty irritated, because the troubleshooting for it in the manual is in the starting section (despite not affecting the starting circuit), instead of the ignition troubleshooting guide. I've attached pictures of it, it's a black little cube with connectors under the tank on the left side of the bike. So I just bypassed it and twisted the red/white wires together and now it has no issue starting anymore. I had thought it might have been the side stand relay, but it had already been disabled by a PO by removing the black/white wire from the TCI box (it's not even in circuit diagram confusingly). Wanted to post this so if anyone in the future with an '82 DOHC bike has this problem to try bypassing this relay, or replacing it (seems available for ~$65), though I'll probably not bother as I always leave it in neutral on the center stand when I'm done riding.

    Attached Files:

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