# Bicycle 2 stroke 80cc motor problems



## pyrotech1987

I bought an 80cc motor kit off ebay from "boygofast" 

80cc Bicycle Engine Motor Kit Motorized bike silver small mount slant head Z80S

and have been having problems and I would like to figure out the solution before I blow the motor the motor. when I first started it (stock carb) it would run for a while (3-4 blocks) then it would rev and take off only to bog down (sounded like it was flooding) and die so I took the carb apart cleaned it good and put it back on. same thing so I bought a new carb off ebay from "nationwidestores"

CNS High Performance Carburetor for 80cc 66cc 48cc Motorized Bicycle


with a fuel/air control. it started acting like it was starving and wouldn't start. finally got it started and am back to square 1 with a twist. now when I first start it each day it doesn't want to warm up very easily and when it finally does it will accelerate fine go for a while (3-4 blocks) then it revs and take off only to bog down (sounds like it's flooding) and die.

today I ran a ways pedaling when the motor died finally after about 8-9 miles It ran hard for about 1.5 miles and the kill switch did not do anything. anything other than wide open throttle and it bogged and died I have adjusted the fuel pin and jet screws. any ideas would be helpful. also my carb when it does decide to go tends to fall off and I have it tightened as tight as it can be.


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## pyrotech1987

now it seems to be running ok it wont idle and is spewing gas out the overflow on the bottom of the carb bowl


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## pyrotech1987

and now its back to running around 100 feet and then it dies


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## chuck_thehammer

have you checked the gas tank VENT... if the vent is clogged . it will run fine for a while . then rev up as it leans out... then dies..

also if the vent is clogged and the tank gets pressurized .. from heat or SUN.. that will flood the carb...


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## sboricic

pyrotech1987 said:


> I bought an 80cc motor kit off ebay from "boygofast"
> 
> 80cc Bicycle Engine Motor Kit Motorized bike silver small mount slant head Z80S
> 
> and have been having problems and I would like to figure out the solution before I blow the motor the motor. when I first started it (stock carb) it would run for a while (3-4 blocks) then it would rev and take off only to bog down (sounded like it was flooding) and die so I took the carb apart cleaned it good and put it back on. same thing so I bought a new carb off ebay from "nationwidestores"
> 
> CNS High Performance Carburetor for 80cc 66cc 48cc Motorized Bicycle
> 
> 
> with a fuel/air control. it started acting like it was starving and wouldn't start. finally got it started and am back to square 1 with a twist. now when I first start it each day it doesn't want to warm up very easily and when it finally does it will accelerate fine go for a while (3-4 blocks) then it revs and take off only to bog down (sounds like it's flooding) and die.
> 
> today I ran a ways pedaling when the motor died finally after about 8-9 miles It ran hard for about 1.5 miles and the kill switch did not do anything. anything other than wide open throttle and it bogged and died I have adjusted the fuel pin and jet screws. any ideas would be helpful. also my carb when it does decide to go tends to fall off and I have it tightened as tight as it can be.


I own one too and have been getting most of my answers from http://motorbicycling.com/forumdisplay.php?f=34

Mine was doing something quite similar...it would start up okay but when I hit the throttle in would bog down and wouldn't have any power. Plus there was oil/gas coming out magneto cover. So I guess I have a bad crankshaft seal causing it to loose air and not letting the magneto work properly.


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## chuck_thehammer

a 2 cycle/stroke engine is extremely sensitive to leaks in the crankcase/seals..

to the engine its like the carburetor is LOOSE... as the crankcase is part of the intake system.


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## pyrotech1987

> have you checked the gas tank VENT... if the vent is clogged . it will run fine for a while . then rev up as it leans out... then dies..
> 
> also if the vent is clogged and the tank gets pressurized .. from heat or SUN.. that will flood the carb...


the engine will run again after coasting for a while and the gas cap has the vent and It is clear

Other than that I have check for air leaks and there are none some other suggestions that have been given to me are running a 40:1 gas/oil ratio and a strip of aluminum can as a spacer for the carb


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## chuck_thehammer

at this point .. order a rebuild kit.. something in that engine is leaking... vacuum.


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## sboricic

Have you tried taking off the muffler and cleaning it with oven cleaner to see if it is clogged? I'm not sure this would be a problem but could be affecting it some way or another.


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## geogrubb

Sure sounds like an air leak, I haven't read how you checked for leaks, while the engine is running spray/dribble some carb/brake parts cleaner behind the carb and along all crankcase mating surfaces, if the engine tempo changes you have found your leak and can take the appropriate action. Have a good one. Geo


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## pyrotech1987

it is running ok now but tops out at around 20 and I am pretty sure it is an air leak that I cant fix so will be buying a new block. In an attempt to fix studs that broke off at the block there were some extra holes drilled in it. In the repair process the main gasket has been ruined but the block is not able to be taken apart so now I wait to buy the new block


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## rlawhon

*80cc Motorized Bicycle Carburator Trouble*

I have a 80cc Motorized Bicycle with Carburetor Trouble.
The carburetor will not stay tight on the intake manifold. I have tighten it as much as possible. It seems to vibrate loose after a few minutes. Is their a fix for this?


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