My new PK 80 suddenly won't accelerate

Discussion in 'Motorized Bicycle Trouble Shooting' started by Jimigunne, Apr 4, 2009.

  1. Jimigunne

    Jimigunne New Member

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    On first test ride, the engine ran good. Made a couple of trips up and down the block. got full acceleration. The engine chain installation was shaky, so it sat unused for only 1 week while redoing the engine chain (ended up removing tensioner). On test ride now, the engine starts every time, but it will not accelerate at all from a low idle. After about 5-6 seconds, it dies. I can see the line going into the carb is full of fuel. Also, throttle feels the same, and as I go from idle to max, the tone of the engine changes a little, but not speed. Experimented with idle screw adjustment and throttle adjustments but no luck. How can the gas go bad in a week? Still, should I dissasemble and clean out carb?
     
  2. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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    What does the Chinese plug look like?
     
  3. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    These might be stoopid questions... Is the fuel turned on? & is the choke off?? (choke lever down)
     
  4. Norman

    Norman LORD VADER Moderator
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    look your carb over you might of had the main jet tube come unscrewed you will need to take off the float bowl to see. Or the throttle slide is not moving take off the air cleaner to check. Is the air cleaner nasty with excess oil?
    The choke could be comming loose and staying on.
    Just some of the easy things to check.
    I think you fuel is more than likely ok.
    here is a champion spark plug that will work L78C
    16 to 1 mix or 20 to 1 mix will work fine for breaking it in.
    stock plug wire should be fine check to make sure that the ends are on tight,if it pulls loose clip off about 1/4" on the end and reinstall it.

    Norman
     
    #4 Norman, Apr 4, 2009
    Last edited: Apr 10, 2009
  5. Jimigunne

    Jimigunne New Member

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    What does plug look like? I don't know....just like all spark plugs look. except it has a threaded post connection. I think I will try to match it up with a new one at Autozone, and see if replacing it helps. I don't know what part number in champion or Autolite, etc. to ask for. I did NOT mix the oil 20:1. Its a 16:1 mix because I read that these engines should have an initial mix of 16:1 until broken in, then use 20:1. Oh yes, BTW...choke has been tried in varous positions, and fuel valve is open. Thanks, Jim
     
  6. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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    You'll need to remove the plug after a hot run and look at the business end. Is it dry brown? Wet black? Glazed gray?
     
  7. Jimigunne

    Jimigunne New Member

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    The plug has dry thin black deposit on it. No part store in town could match the number on plug up with a replacement! One place was able to match up the bore size, but all the ones with right bore size have the usual thick brass snap-on electrical connection. This one just has the thin threaded post. I suspect any plain old lawnmower-type plug would work. I can't think of some way to spin the engine up to actually test the spark with plug out and outer part grounded with a jumper clip to engine ground. (without having a dynamometer to put the rear wheel on that is). Thanks, Jim
     
  8. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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  9. europorsche914

    europorsche914 New Member

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    Im bettin either the main jet came loose or you have an air leak, definitely sound like a lean condition if the throttle is opened, more air & fuel enter the engine but the leak may get worse adding even more air to the engine, air leak + normal metered air + normal metered fuel = alot of air + normal metered fuel == LEAN! Check the carb-manifold connection, manifold-cyl connection, cyl-head connection. Good Luck! -Justin
     
  10. Jimigunne

    Jimigunne New Member

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    Well, I am OK with the 16:1 break-in mix?
    thanks, Jim
     
  11. brandongordon2002

    brandongordon2002 New Member

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    Hey guys my i have a question about the PK-L80 kit. My first build was an engine from tsunami bikes loacted in hamilton ontario and it does 55km/h and accelerates really good. Im blown away by the performance. A few months later i found someone who was selling kits for 105.00 and they were the PK-L80 kits upgrade kits. I decided since they were so cheap i would start selling+installing them on bikes. I have build over 6 bikes and none of them have anywhere near as much power as mine. The acceleration sucks and the kits have no power band. Anyone think these could be knockoffs? They claim to be 800 PK-L80 upgrade kits selling for 105.00. What could be the problem?
     
  12. boz_m

    boz_m New Member

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    check that your kill switch wire from the engine isnt touching the engine. I had the same problem, thought i was going crazy, took everything apart.
     
  13. Alson333

    Alson333 New Member

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    So what happened to the PK 80? I heard bad things about the PK L80 something about the bottom end crank out of aling or something from BoyGoFast
     

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