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Difficult hot starting problems.

Discussion in 'XJ Technical Chat' started by jim123, Jun 27, 2012.

  1. jim123

    jim123 Member

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    I have a 650 Maxim. Valves are in spec, carbs rebuilt recently, synced properly, in line fuel filter. It starts fine cold but if I have it warmed up and shut it off for a few minutes, it cranks and does not want to start. It just started acting this way when the outside temps got into the 90's. Any ideas what to do first?
     
  2. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Check the water level in the battery.

    Keep an eye on the oil level.

    Put the petcock on PRI for about 30 sec before attempting to start. As soon as it fires, go back to ON.

    How badly out of spec were the valves before you got ahold of it?

    Have you done a compression test recently?
     
  3. RickCoMatic

    RickCoMatic Well-Known Member

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    After an initial Cold Start, ... the Bike should Pop when you touch the Start Button.
    No Choke (Enrichment)

    Throw a set of Plugs in it.
    That always puts some new life in my bike.

    Make sure the Air Cleaner isnt clogged.
    Visit the Alternator Brushes. 10mm (Min.)
    Scrap the OEM Fuse Panel for a New Model.
    If you are running a Inline Gas Filter ... make sure its letting Gas flow to the Carbs.
     
  4. jim123

    jim123 Member

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    I did the compression test 4000 miles ago and they were all between 151 and 154. At the time one exhaust valve was right at the tight limit. 4000 miles later all the clearances were the same as before but I fixed the one tight one and it is out of spec by about .002" loose. Before the adjustment, when the engine was hot, it was right at the min limit and when it cooled down to 45 degrees in the garage overnight, it became .001" too tight. After the fix, I can hear it clicking away now when I ride.

    This is the 5th season on the battery that came with the bike. Not sure how old it was then. It seems to spin the engine pretty fast but I have to release the started button at just the right time to get the bike to stumble to life on some of the cold startups. Is there a min voltage reading I can measure at the battery to tell if it's still good?
     
  5. RickCoMatic

    RickCoMatic Well-Known Member

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    This is a clue to maintenance you need to do:

    1. "I have to release the starter button at just the right time to get the bike to stumble to life on some of the cold startups."

    Check your Starter.
    Inspect the Brushes for Minimum Length.
    Douche the Commutator and Housing free of Carbon Dust.
    (The Carbon Dust comes from the Brushes,... That's why you'll likely need that Starter's Electrical-end douched and might need new Brushes.
     
  6. bkerby

    bkerby Member

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    Sounds like a dying battery and or bad plugs
     
  7. RickCoMatic

    RickCoMatic Well-Known Member

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    You can bring-in a Fully Charged Battery to AutoZone and they will perform a Test to determine its :::> CRANKING AMPS <::: for free.

    12 Volts isn't the Value you need for running that bike.
    Amps is the story.

    It's possible that the Battery is using all its power just to crank-over the Starter with nothing in reserve to run the Bike.

    Out-of-specs Brushes won't keep the system topped-up.
    You live off the top of the Battery until the current drops below whats needed to run the bike.
    Then, you stall and let the Battery recover a little bit for another 15 minute spurt.
     
  8. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    The fact that it fires when you let go of the button is the giveaway to this condition.

    It's possible for the battery to be strong enough to quite vigorously spin the motor, while not having enough power left for the ignition. I would never have believed this until it happened to me (more than once.) Your battery is dying or the bike is failing to keep it fully charged.
     
  9. RickCoMatic

    RickCoMatic Well-Known Member

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    I really think you should:

    !.) Have the Battery tested for Cranking Amps.
    2.) Visit the Alternator Brushes and Inspect the Alt. Rotor.
    3.) Visit the Starter Electrical-end.
    a.) Clean
    b.) Measure Brushes

    You can "Dress" the Alt Brushes Orbit Paths on the Rotor with a Old Style Typewriter Eraser. (The famous Wheel and Brush type). The pumice will remove arcing buildup and shine the surface of the Rotor.

    Your Bikes Charging Output should be +14.2 -to- 14.5VDC @ 2000rpm's and above. Below 14.2 fails to sufficiently charge the battery. Above Specs "Cooks" the Battery dry.
     
  10. dubyaohohdee

    dubyaohohdee Member

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    Wouldnt all of the suggestions discussed so far also affect cold starting? My bike is the same. Cold start is perfect. Hot start takes 4 or 5 seconds and then the bike stumbles to life.
     
  11. RickCoMatic

    RickCoMatic Well-Known Member

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    There is a myriad of reasons a Bike won't start-up ... "Hot".

    But, ... because you say it fires right-up, ... cold ... that points to Mixture.

    Although by no means certain, ... given the two clues I'd suspect that your Pilot Mixtures might be too Rich.

    She fires COLD.
    Not HOT.

    You may be too RICH, ... BUT ... not very much.
    If it Idles steadily and doesn't "Hunt", ... Check the Plug Color.

    If their Chocolate Brown or Darker, ... Turn the Mixture Screws IN a few DEGREES <---
    (Don't go beyond the width of a Nickel. Tweak; only!)
     
  12. jim123

    jim123 Member

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    Hot start problems go away if I give it a little throttle while it cranks. It fires right up this way.
     
  13. RickCoMatic

    RickCoMatic Well-Known Member

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    Opening the Throttles to facilitate the Hot Start might be just adding a bit of AIR before it really starts pulling.

    Plug Chop or ColorTune.

    When its Hot, ... you should just have to hit the Start Button and have it fire-up.
     
  14. jmilliken

    jmilliken Well-Known Member

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    You said the battery was 5+ years old. Stronly recommend replacing that.
     

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