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Thread: K75S won’t start

  1. #1
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    Aug 2006
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    Grand Rapids, MI
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    K75S won’t start

    1986 K75S, 61xxx miles, cranks but won’t start. Stopped for gas while out for a ride, after filling up the bike didn’t immediately start but after a few attempts it started and ran for about 20 seconds then died and wouldn’t restart. It cranks over but doesn’t start. After getting the bike home I checked that the fuel pump runs, preemptively replaced the fuel filter, checked fuel flow from the fuel rail, pulled the spark plugs, found them to be wet and found cylinder 1 wasn’t getting spark; swapped plugs, plug wires and coils, no spark on cylinder 1. Checked the HES, getting continuity between pin 14 of the Montronic connector to the primary connector of #1 coil. Before I start pulling apart the wiring harness looking for a partially open wire I want to ask here for what I may be missing.
    lostandwandering
    87 K75S, 2013 F800GT

  2. #2
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    Grand Rapids, MI
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    K75S won’t start

    Forgot to mention 13.02 volts from the battery.
    lostandwandering
    87 K75S, 2013 F800GT

  3. #3
    Anytime a K75 fails to start I do two things:
    1) Disconnect and reconnect the connector to the LJetronic ECU a few times. **
    2) Remove and dry the spark plugs.

    However, since this happened at fuel-up there is a very strong possibility that you got a dose of water in the gas. Isoheet in the red bottle - 1/2 bottle in the tank would be my next step.

    ** How I learned about #1 above. Bike failed to start. No spark. Erratic injection. Stored bike. Rode 689 miles two up. Drove truck and trailer rig 689 miles to get bike. Drove with bike on trailer 689 miles home. With bike still on trailer in condo parking lot did a little more troubleshooting. Looked to see if I could find corrosion or a problem with the ECU connection. I saw none. But as soon as I reconnected the ECU and tried to start the bike it started and ran fine and is still running fine three years later. My most embarrassing troubleshooting failure of all times.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  4. #4
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    Aug 2006
    Location
    Grand Rapids, MI
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    Thank you Paul, that combination did the trick though I drained and dried the tank before refueling. I hadn’t heard about repeatedly resetting the FI control connector. Any rate that combination worked. Thanks again for another enlightening post.
    lostandwandering
    87 K75S, 2013 F800GT

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