Bike starts ok then dies down

Discussion in '2-Stroke Engines' started by Alexmeow, May 25, 2016.

  1. Alexmeow

    Alexmeow Member

    My motorized bicycle is an 80cc kit off eBay and I've been having trouble with it ever since I got it and when I thought I finally fixed it now it has a complete loss of power after about 15 seconds meaning it's top speed is like 8 mph and it can't go up any hills to save its life not even small ones I tried replacing the cdi and the spark plug thinking it was an electrical problem but really there was still no change the old spark plug was so black I thought maybe it was burnt I hear this is carbon fouling and I'm trying to keep the new one from getting like and I've been told it was running too rich so I moved the c clip in the carb to the top peg and use gas at at 32:1 ratio and still no change after long rides the carb sometimes drips out a black hot liquid which I think is oil I just want to take it to a repair shop but we don't have any of those for these in New York (that I know of) and the weird part is it was working just fine the day before except for a flat tire I managed to make it home on since it was a slime tube that kept leaking air and had to be pumped up every couple minutes until it seated properly then the next day I go to ride it and this
     

  2. Frankfort MB's

    Frankfort MB's Well-Known Member

    Have you checked your exhaust cap to see if it was full of oil
     
  3. Alexmeow

    Alexmeow Member

    I took off the exhaust pipe once and tried washing it with some water but that's about it
     
  4. crassius

    crassius Well-Known Member

    are you starting it with the choke on and it dies when you take the choke off? or starting without choke and it dies as it starts to warm up? both of these can be carb/intake problems

    if any oil is showing up near head gasket, that can be head studs loose
     
  5. Alexmeow

    Alexmeow Member

    The only oil is at carb and exhaust pipe and I start it with the choke completely open closing it doesn't let it reach full speed before it dies off on its own anyway

    (Edit: I found some oil in the magneto compartment when I went to open it it was missing a screw too)
     
    Last edited: Jun 2, 2016
  6. Alexmeow

    Alexmeow Member

    It starts fine but then after it warms up it just wants to die and I have to keep pedaling to keep the motor working at full throttle doing nothing for the engine Kuz anything less then full throttle it dies
     
  7. crassius

    crassius Well-Known Member

    sounds like your fuel may not be flowing when it runs - sometimes the vent in the gas cap isn't working - try it with the fuel cap off - another thing could be that too much vibration at the carb is foaming fuel in the bowl, make sure everything is tight and steady there and at motor mounts
     
  8. Alexmeow

    Alexmeow Member

    When it was working normal there were hardly any vibrations at all now the engine shakes a lot and the whole ride is very vibraty/bumpy the engine is very tight when I first got it I made sure to tighten everything so these new shakes mystify me
     
  9. Alexmeow

    Alexmeow Member

    Now that I think about it that might be the problem because I know sometimes when I would fill it it would over fill by accident and nothing leaked out so it probabaly clogged the gas cap I'll wash it out and test it in the morning
     
  10. Alexmeow

    Alexmeow Member

    Nope didn't fix it I'm thinking I'll just have to buy a new engine I just can't figure out what's wrong
     
  11. crassius

    crassius Well-Known Member

    if you find the shaking, you may solve the problem - don't forget to check for frame cracks and broken mounting studs
     
  12. Frankfort MB's

    Frankfort MB's Well-Known Member

    Check your spark plug color... I leaned my mixture out and it stopped vibrating as much as it did
     
  13. Eric Cherry

    Eric Cherry Guest

    im having the same EXACT problem
     
    Last edited by a moderator: May 30, 2016
  14. Alexmeow

    Alexmeow Member

  15. Frankfort MB's

    Frankfort MB's Well-Known Member

    Or the cdi, spark plug, anything electrical lol
     
  16. crassius

    crassius Well-Known Member

    been a mechanic for a whole bunch o' years and it took maybe 4 months working on 25 or 30 of these before I was seeing everything I was looking at - for a new user, it is best to spend much of your time reading here and looking at pics to try to get a feel for these, rather than tearing them down and replacing parts which can make the problem worse

    not often that a quick google will fix it
     
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