pocket bike keeps cutting off:(

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ipwnr

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ok so i hove 4 pocket bikes they are all 49 cc engines and after i start them they just cutt of and all of them seem to have the same symptoms the engines r ok and compression is great and also it will idle and then just cutt of after a minute. can any one help find the problem?
 
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@S&Scustoms im pretty sure its not the timing because it will rev full speed and cutt off or sometimes it will start bogging nd then cutt off but thx ill try that!
 
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@r97 its all stock and @bluethunder3320 yes its all float style carbs and is there any way i can get ride of the float??
 
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i bought it a new fuel line also and its a carby problem. o and the guy who sold me the bikes said it has ben sitting in his garage for a year and there was fuel in the tank for that period of time.
 
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sexyvicta

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pull the plug next time it stops. Check to see if its wet , dry or gummed up with black stuff. Will help narrow down your problem.

also there is an outside chance you do have a bad plug. Have heard of plugs(mostly ngk) that will stop working once they get hot for no aparent reason.

also consider crankcase leaks. When the engine is hot the leak will be worse than when cold.

edit:

S&Scustoms said:
hi man well so it starts and cuts off you timing on you flywheel might be the prob

check this vid out on setting the spark on your pocket bike
Click to expand...

yeh i had a twostoke mower that was sometimes hard to start and then ran well but would mysteriously cut out and then not re start once in a while. Checked and replace everything before i finaly pulled the engine off the body to check the flywheel / magneto clearance. Closed it to 10 thou and its been running perfect for 6 months now.
 
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@sexyvicta i pulled the plug out after it shut off again and it was dry and when it shut off the first thing i did was rush to the fuel shut off valve and when i took the little screw out under the float bowl gas rushed out and also when i turned over the engine when it was cold it would have good compression but when i did it again when it shut off there barley was any compression.
 
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sexyvicta

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that sounds less than ideal haha

iduno man i have no idea what type your engine is... but when you said compression, were you refering to combustion chamber or crankcase? or just how it felt as ur turned it over?

so your carb float bowl was full of fuel when the engine stopped?

check/clean main jet first i guess. If theres nothing wrong with your carb then i guess your engine ain't sucking in fuel :(
 
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@sexyvicta its a daymak brand pocket bike or something along that and by compression i mean when i turn the flywheel when the engine is cold i can feel the flywheel bouncing back and when its warm it didnt bounce back and yes the bowl was full of fuel when the engine stoped
 
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sexyvicta

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ah well you might need to find someone who has experience with your engine or at least twostrokes in general. Somebody who can look at it in person would be best...maybe a racing kart shop?

here are some of my ideas which may be of use/probably not:

I dont think your problem is spark seeing as the plug was dry and your float bowl was full. For some reason your gas isn't moving from your float bowl into your engine.

First of all check your main jet again. Then check that there are no air leaks between the carb and engine. You could always check the exhaust port and muffler...i doubt it is the problem but maybe if it is reallllly blocked up it could cause issues(the engine wont be able to blow out burnt charge and suck in the fresh stuff...i've never had one so blocked up that the engine wouldn't run but have had the port gummed up enough that the engine wouldn't run at wot.)

but realy if everything is good on the outside of engine then you will have to test combustion chamber and crankcase compression...or just pull the engine apart (if you have low compression then you will have to do it anyway haha).

Couple of tests you can do if you dont have the gear to test compression are:
- turn the engine over by hand(slowly with throttle open) how many many times do you feel a resistance/compression per revolution of the engine? you should be able to feel one strong(combustion chamber) and one weaker(crankcase).... edit: this method works best when you have a known good engine to compare it to.

another test you could do is to try running the engine with no exhaust and airfilter. This can take some pressure off leaky seals. Ive had lawnmowers that have veeery low compression but will start and run if i remove the muffler haha
 
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