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Thread: 85 K100RS 195,000: Intermittent Off/On/Off in mountains, Sporadic Flooding on Start.

  1. #1
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    85 K100RS 195,000: Intermittent Off/On/Off in mountains, Sporadic Flooding on Start.

    LE Jetronic Fuel Injection:
    Just returned to Phila. from 7,500 mi. MOA SLC rally trip. Three times off/on/off while running hot, hard and high: 285N into Alamosa CO, Pikes Peak in traffic, I70 Vail Pass. Fourth time stopped for high water temp light coming on, 139N to Rangely CO. All fixed by waiting 5 minutes. Another time tach went dead 5 min. Into ride. Dose of Stabilant 22 on K1 connector fixed for the rest of the trip.

    Three times flooded on startup, once cold, SLC, two hot, WISC. & PA. Jumper cables to car battery let me restart after a lot of cranking. It also flooded on a cold start last winter.


    The throttle position sensor (TPS) does 2 things, it suddenly stops the fuel above 2000RPM when you close the throttle and it “floods the cylinders” when you ask for full throttle.

    Can a faulty Throttle Position Sensor or, corroded or bad wires in its wiring cause intermittent sudden, severe off/on/offs?

    Can it cause rare start up engine floods?

    I used the high altitude jumper above 4000’. Used best gas I could buy, often 91 octane without ethanol. I added dirt bike temp sensor placed near computer in gap between under tank and ahead of tool area. Bike worked fine in PA reading 137 deg F. The highest I saw.

    The computer seems to be fine, the temp sensor and fuel pressure regulator were replaced recently (~5 yrs ago). Much of the time it runs very very well. One tankful late in the trip seemed a little rough for 35 miles after a 2 gallon fuel fill but suddenly smoothed out for the rest of the tank.

  2. #2
    Registered User dieselyoda's Avatar
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    Check your ground connections. Pull the fuses and reinsert.
    1997 R1100RT, 1981 KZ 440 LTD, R80RT, R90/6 sidecar, K1100RS,1983 K100RS (Cafe now)

    “The major civilizing force in the world is not religion, it is sex.”

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    OP here

    Thanks for tips.

    I removed and reinstalled my fuses with some extra sliding in and out.
    I have addes a double ground wire and they are tight.


    I bought a new Bosch Throttle Pos. Sensor and put it in,$90. According to the Youtube that shows its guts it should not help, we'll see if that microswitch signal was somehow bouncing when it wasn't near bottom of throttle.

    I think sudden loss of power, sudden return, then repeating randomly is due to corroded contacts that handle MILLI VOLTs, not 12 volts, not a relay, not related to hitting bumps. Seems warm up or heat related.
    It runs great a vast majority of the time.


    I wonder if every time it has flooded on startup, if I cranked the throttle all the way around and if it "added more gas on full throttle" even when the motor isn't quite running yet.


    Comments welcome.

  4. #4
    Rally Rat Roc-Roc's Avatar
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    I love my 85 K100RS it was still running with over 220k miles when I reluctantly sold it. Is the plug seated into the computer that's sits above the battery.
    ROC-ROC

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    Orig Poster OP

    The big computer K1 plug is treated with Stabilant 22 (NAPA CE-1) and seated, meaning far enough in to have the spring steel clip/latch catch, the latch that gets released through a hole in the bottom of the tool tray.

  6. #6
    Registered User dieselyoda's Avatar
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    Pull your injector connectors, all of them, when its hot. Use an analog voltmeter on the ground/ecm side of one of the injector connectors. Crank engine over. Your meter should jump but not hold steady.

    If it holds steady, then you have more to look at.
    1997 R1100RT, 1981 KZ 440 LTD, R80RT, R90/6 sidecar, K1100RS,1983 K100RS (Cafe now)

    “The major civilizing force in the world is not religion, it is sex.”

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    OP here: Love the result

    Dear 2 Valve K bike folks, maybe 4v too,
    Having a brand new Bosch Throttle Position Sensor (TPS, $90) seems like magic for 300 miles now.

    Youtube link about function and testing: www.youtube.com/watch?v=7-_ORQ-Gsmg

    I see it just has a microswitch inside to shut off the fuel at zero throttle when above 2000 RPM and something like a set of points to tell the computer to flood in some extra gas at full throttle twist BUT now my bike loves to leave stop lights and signs and it it loves to be called on to accelerate from most any RPM. I suspect that a very old TPS was sending "unauthorized" signals to the computer to turn off the fuel suddenly for short or longer durations and I think it told the computer to flood fuel sometimes, like some startups and sometimes when gas tanks seemed to run out well before nearing 200 miles.

    I'm very happy with my old bike now. I'll post again in a month or two unless it has a relapse. then I'll post rapidly.

    Happy near Philly PA.
    85 K100RS 195,000+ miles
    Last edited by 075038; 08-07-2017 at 12:51 PM.

  8. #8
    Registered User 58058D's Avatar
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    Glad you got it taken care of. New TPS sounds like the ticket!
    Jim Douglas '00 K1200RS >138,000 miles -- Black, 01/10/2000 to present
    Gone: White '09 K1300S sold @ 22k mi, Black '93 K1100RS traded @ 78k mi, Red '85 K100RS sold @ 44k mi, '06 Kaw 650R chrome yellow track bike sold http://www.seagullbb.com/

  9. #9
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    85 K Bike Flooding at start gone

    Original Poster Here:
    My 196,750 mi. 85 K100RS has started and run great since the new TPS even when 30 - 50 deg. F.

    I dare not crank the throttle to full when starting knowing that full crank can sometimes tell the computer to give full gas.

    When not started for a day, I use the artificial choke on full which, with my old cable, does not lift the throttle the full "shim" amount, so as I crank I rotate my throttle slightly and slowly.

    The first little bit of rotation just takes up the slack to the artificial choke, then the throttle rotation starts to lift the throttle the amount that a new choke cable set properly would do. It starts, in less than 3 or so seconds of cranking, like my 50,000 mi. 1990 K75S.

    Next thing to fix is the trip meter. Resetting at gas fill ups takes tens digit spinning and spinning to get the zero to come around.

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