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Thread: 85 K100 Cold Start - Air Temp Sensor?

  1. #1
    Fred Trimble
    Join Date
    Mar 2009
    Location
    Royal Oak, MI
    Posts
    87

    85 K100 Cold Start - Air Temp Sensor?

    So, the '85 is showing some age. I've tried to start several times in the last few days. At ambient temps above 70 deg. F, it starts right up - 1-2 cranks and it's good. Below 50 deg. F, it will crank without the slightest interest in combustion. Yes, I'm using the 'choke' lever. I see in my Haynes manual that there is an air temperature sensor in the air flow meter. The manual states 'No information is available to assist the ordinary owner to test this component'. So, am I on the right track? Time to buy another air flow meter?
    Fred Trimble
    1985 K100RT
    2009 R1200RT

  2. #2
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    4,819
    Fred,

    Before you go too far, check the gap on the spark plugs. I believe they should be .024-.028". Quick and easy to do. If the gap is really wide, it would be hard to start in cold temps.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  3. #3
    Everything has to be right to start a Classic K when it is cold outside: all sensors in spec, correct fuel pressure, clean connectors, and correct idle mixture adjustment. This needs to be done while synching the throttle bodies and, ideally with an exhaust gas analyser. To get good readings requires clean oil and a fully warmed engine.

  4. #4
    Mars needs women! 35634's Avatar
    Join Date
    Apr 2008
    Location
    SW Ohio
    Posts
    2,157
    Completely off topic, It looks like you joined the MOA back in '85, about 41 persons after I joined!
    1987 K75S
    Original litter
    Original owner
    2012 Ural Gear Up

  5. #5
    Fred Trimble
    Join Date
    Mar 2009
    Location
    Royal Oak, MI
    Posts
    87
    All advice is appreciated, but just to be clear on the symtoms -

    1) I've owned the bike since 1985
    2) I know how it behaves during cold weather
    3) At 65 Deg F this morning, there was no combustion - no 'tryin to start', no 'a couple of bangs but not quite catching', nothing but strong cranking
    4) At 70 odd degrees this afternoon, it cranked twice and ran immediately and smoothly.
    5) It's repeated this temperature related behaviour 3 times in the last week
    6) I started at 52 Deg this morning and tried every hour or so until it fired
    7) I just went out and it started immediately - it's currently 72 Deg
    8) All ambient temps per the weather app on my smart phone for local weather

    Thaks for any help anyone can give me on this.
    Fred Trimble
    1985 K100RT
    2009 R1200RT

  6. #6
    Registered User
    Join Date
    Apr 2005
    Location
    Rapid City South Dakota
    Posts
    243

    Try this

    The only time I had a no-start problem with my 85 k rig, I solved it by switching computers between my two K's. They both started instantly. I determined that the act of disconnecting the computer cleaned the contacts. Disconnect and connect the computer a couple times. It is worth a try and costs nothing.
    Harold In Rapid City, SD
    1985 K100RT Bullit
    1985 K100XX/EML Bemel

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