Bike starts ok then dies down

Alexmeow

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Mar 18, 2016
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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
 


crassius

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Jul 23, 2012
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4,575
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
 

Alexmeow

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Mar 18, 2016
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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)
 
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Alexmeow

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Mar 18, 2016
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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
 

crassius

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Jul 23, 2012
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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
 

Alexmeow

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Mar 18, 2016
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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
 

Alexmeow

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Mar 18, 2016
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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
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
 

Alexmeow

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Mar 18, 2016
Messages
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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
 
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