1987 JS550 Stop Switch Relay Operation
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  1. #1
    PWCToday Newbie SonomaGTLS6's Avatar
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    1987 JS550 Stop Switch Relay Operation

    Long story short, my ski is a 1987 JS550 that I received in pieces and traded a 6 pack of Oberon for 7 or 8 years ago. After an engine rebuild and some TLC itís given me years of pleasure with the typical small fixes here and there to keep it running well.

    Then this year I take it out and it starts but then dies after 2 sec to 5 min of running. Flat out dies, no stumbling, no restart unless engine completely stopped. Not bad gas, not a bad battery and all grounds/connections are good. Stop switch relay right?

    So I take apart my ebox tonight and it looks like a relic from the Edmund Fitzgerald inside Öcomplete with a slurry of wet red rust.

    682E7B55-85EF-4D25-A736-ED2BDAC4E6BA.jpeg

    After cleaning what I can and starting to dissect it, I find that the Black/white wire coming from the stop switch relay is pinched between the rectifier and ebox body where the starter relay post exitsÖit makes me wonder if that was being shorted to ground somehow. Then I look at the schematic and canít figure out whether that being grounded or not would actually be a problem.

    Schematic:
    8766319F-A2E7-4B49-A495-ADD7C452D072.jpeg

    So before I dig deeper, Iím wondering if anyone can comment on how the stop switch relay actually works. Does it essentially pull the Black/white wire to ground when the switch is pressed thus disabling the spark? Is there any way to check the performance of the relay while out of the ski? Is it a solenoid or solid state/delayed such that a intermittent switch press results in a latched shutdown without the need to hold down the kill switch?

    Thanks!

  2. #2
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 1987 JS550 Stop Switch Relay Operation

    Motocross bikes, chainsaws, and many other 2 strokes had a simple kill
    switch. Press the button long enough and the engine eventually died.
    But if you released the kill button while the engine was still rotating, the
    engine would restart.

    The original JS400, and JS440 had a mechanical on-off switch. I believe
    that was changed in 1982 when they released the JS550.

    The stop switch relay eliminated the need for the large on-off switch,
    and only required a quick button press to kill the engine. Once the kill
    button was momentarily depressed, the relay was triggered and it shut
    the engine off.

    It might just be a simple circuit with an SCR. I have never replaced one.

    Black with a white stripe is the Kawasaki wire color for the kill switch.

    It is more likely that the ignition coil, exciter coil, or pulser coil is the
    cause. Rust will eventually kill the coils.

    Take a pair of old spark plugs, and bend the bridges back completely,
    and test for weak spark.


    Bill M.

    An A/C voltage test on the stator's ignition coils is a better test than
    an ohm test.
    Horsepower == Speed, RPM != Speed



  3. #3
    Frequent Poster heresjohnny151's Avatar
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    Re: 1987 JS550 Stop Switch Relay Operation

    A quick and easy way to see if it is the stop/.relay is disconnect the relay connectors inside the electrical box. Then turn your idol screw so the motor will turn off by itself by just taking your finger off the throttle. The reason to set it up so it dies is because once you disconnect the relay connector you would have no way to shut the motor off.I think what is happening to your ski is the stop relay is shutting off by itself and staying in the off mode until it all the sudden changes back on its own. So you could still go ride your ski with out buying a part, but your ski will die whenever your finger comes off the throttle. All racers back in the 80's and 90's had to race with no idle set otherwise they would be DQ. I about 90 % sure this is your problem. You will know the first time you ride it if it fixed your problem because you said it would shut off in 2 sec to 5 min.

  4. #4
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: 1987 JS550 Stop Switch Relay Operation

    I have good used oe stopper relay if you want

  5. #5
    PWCToday Newbie SonomaGTLS6's Avatar
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    Re: 1987 JS550 Stop Switch Relay Operation

    Hey guys thanks for the responses - for posterity sake I bypassed the stopper relay by wiring it so the grounding the coil usually did goes directly thru the stop switch. So essentially to shut it down I have to hold down the switch or remove the lanyard (added lanyard when I first bought it for auto-shutdown when falling off).

    Now of course almost a year later my starter solenoid took a crap (clicks but no crank) so it looks like I need to replace that…the joys of finding the weakest link each year!

  6. #6
    PWCToday.com Is My Home Away From Home Bionic racing's Avatar
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    Re: 1987 JS550 Stop Switch Relay Operation

    Have those

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