80cc 2 stroke motorized bicycle bike problem help

josh12a

New Member
Dec 1, 2018
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So, my 80cc 2 stroke motorized bicycle bike runs normally for 7-10 minutes but then it starts to jerk and the thing starts to shut off and can't turn back on. (it feels like gas isn't going through properly)

But then a day later, it worked again! but the same problem happened!!

HELP
 

RickM

New Member
Nov 30, 2018
7
5
3
Check to see if gas is mixed? Getting hot? Still have compression and turning over normally when trying to restart after it dies?
 

RickM

New Member
Nov 30, 2018
7
5
3
So, my 80cc 2 stroke motorized bicycle bike runs normally for 7-10 minutes but then it starts to jerk and the thing starts to shut off and can't turn back on. (it feels like gas isn't going through properly)

But then a day later, it worked again! but the same problem happened!!

HELP
You might check your gas line for an air leak, had an old Harley would start then would die after it ran the fuel line out before it started sucking air....
 

allen standley

Well-Known Member
Oct 22, 2011
1,120
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Bangor, Maine
Sounds like Gas Cap not venting. Get it going again and leave the cap loose. See if she runs longer then. In my beginnings this was always an issue. I even now drill a tiny hole 3/32 in the center of the gas cap on Every Build.
 
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RickM

New Member
Nov 30, 2018
7
5
3
Sounds like Gas Cap not venting. Get it going again and leave the cap loose. See if she runs longer then. In my beginnings this was always an issue. I even now drill a tiny hole 3/32 in the center of the gas cap on Every Build.
Good to know...reminds me of drilling thermostats before it became the norm....
 

Billsef Laurall

New Member
Dec 14, 2018
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Ive heard about failing CDI's doing this when they get too hot, but I would definitely check out the gas cap like others have suggested.
 

kinopio

New Member
Oct 9, 2020
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I'm having a very similar problem. The bike will usually start then run really rough for about a quarter mile then just bogg out and die. It refuses to restart for several hours and then repeat process. The CDI, magneto, and spark plug are all brand new. The bike was gifted to me by a family friend and they let it sit out for close to a year. I cleaned it up as best I could and only started after I replaced the previously stated parts. It ran great for the first week then failed out of nowhere. I dont know what to do anymore. Youtube only has so much to offer. I am not very mechanically inclined but I've made sure to take care of everything parts wise. Can anyone help?
 

hemmadroid

New Member
Feb 20, 2021
10
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57
So, my 80cc 2 stroke motorized bicycle bike runs normally for 7-10 minutes but then it starts to jerk and the thing starts to shut off and can't turn back on. (it feels like gas isn't going through properly)

But then a day later, it worked again! but the same problem happened!!

HELP
Maybe a kink in fuel line? air filters sometimes choke life from small motors. try taking it off