Difficult/Hard starting 80cc 2 Stroke bicycle engine

Benjamin Cox

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The problem I am having is when I try to start the engine, it takes approximately 10-15 minutes of trying. After that, there's a chance it starts, but what's weird is that i found when I get up to 5kph, dump the clutch, and throttle it, the bike could start when im almost at a complete stop (after trying for 10-15 minutes). i have also checked spark plug and there is a spark.

Worth noting:
i am not running an air filter. when one is attached to carb, there is absolutely no chance of it starting, i tried for weeks until i figured out that taking it off was the correct solution, even when i just tried putting a piece of foam around the air intake, it started to bog down and it couldn't even make it up a mellow hill.
Also when i try to accelerate from a slow speed, the engine makes a somewhat loud squeaky sound.

If any of this information helps to why the engine is hard to start then great!
 

Chainlube

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The problem I am having is when I try to start the engine, it takes approximately 10-15 minutes of trying. After that, there's a chance it starts, but what's weird is that i found when I get up to 5kph, dump the clutch, and throttle it, the bike could start when im almost at a complete stop (after trying for 10-15 minutes). i have also checked spark plug and there is a spark.

Worth noting:
i am not running an air filter. when one is attached to carb, there is absolutely no chance of it starting, i tried for weeks until i figured out that taking it off was the correct solution, even when i just tried putting a piece of foam around the air intake, it started to bog down and it couldn't even make it up a mellow hill.
Also when i try to accelerate from a slow speed, the engine makes a somewhat loud squeaky sound.

If any of this information helps to why the engine is hard to start then great!
A picture of your ride might explain a few things, got one? If it's a hard starting, it can be cheap plug (kit plug) or fuel starvation. Float sticking, or crud in the jet. It's not an air filter issue.
 

Benjamin Cox

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A picture of your ride might explain a few things, got one? If it's a hard starting, it can be cheap plug (kit plug) or fuel starvation. Float sticking, or crud in the jet. It's not an air filter issue.
IMG20220703083152.jpg
IMG20220703083201.jpg
IMG20220703083212.jpg


here are the images of the bike, and yes i know i havent mounted the front of the engine, this question isnt about the mounting.
 

DAMIEN1307

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here are the images of the bike, and yes i know i havent mounted the front of the engine, this question isnt about the mounting.
Start off with the gas filter...its on upside down...Then replace that crappy, Chinese, Z4C spark plug with something that actually works properly and consistently like an NGK-BR6HS spark plug from your local autoparts store...You also have a problem with the cover to the magneto case, it looks like it is tearing itself open from the inside out in the center of the cover pushing outwards, that can't be good...I have old can openers that can't do that anymore...lol.

I also noticed the choke lever in the full up position which should be full choke "on" postion, yet the hole is unobstructed when it should be totally obstructed when the lever is in the up position.
That lever should be in the full down position for that choke to be totally open in the off postion like the pic shows...This tells me that your choke is not even working because of the lever not actuating the choke mechanism properly...No wonder your having problems starting if you do not even have a properly working choke to start with.

And YES the front motor mount IS an issue...Without that being firmly mounted in place, everything else is going to snap, crackle, and pop like a bowl full of Rice Krispies and milk resulting in a catastrophic failure, and duct tape maybe the handymans best friend but is definitely not a suitable gas tank mounting device...lol.

And this is just a starting point from what I see in the pics...Im sure that others will add their observations to this too.
 

DieselTech

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I bet the nut spun loose on the magneto causing a no start or erratic timing resulting in poorly running engine or non-running engine.
The other thing I've seen is the manufacturer puts too thick of lock washer on the magneto, & the nut sticks out too far, & it cracks the cover when you tighten down the 4 cover bolts/screws.
 

Chainlube

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Start off with the gas filter...its on upside down...Then replace that crappy, Chinese, Z4C spark plug with something that actually works properly and consistently like an NGK-BR6HS spark plug from your local autoparts store...You also have a problem with the cover to the magneto case, it looks like it is tearing itself open from the inside out in the center of the cover pushing outwards, that can't be good...I have old can openers that can't do that anymore...lol.

I also noticed the choke lever in the full up position which should be full choke "on" postion, yet the hole is unobstructed when it should be totally obstructed when the lever is in the up position.
That lever should be in the full down position for that choke to be totally open in the off postion like the pic shows...This tells me that your choke is not even working because of the lever not actuating the choke mechanism properly...No wonder your having problems starting if you do not even have a properly working choke to start with.

And YES the front motor mount IS an issue...Without that being firmly mounted in place, everything else is going to snap, crackle, and pop like a bowl full of Rice Krispies and milk resulting in a catastrophic failure, and duct tape maybe the handymans best friend but is definitely not a suitable gas tank mounting device...lol.

And this is just a starting point from what I see in the pics...Im sure that others will add their observations to this too.
Yes all those things are real issues, the one that is most important is the front mount U-bolt, the rest won't keep it from running. First start by removing the mag side cover and see if it has become loose or in any way messed up or broken. Then put a socket on those head studs and see how many are loose, I see some burnt oil on the exhaust. Once you clear all that up, put in a new plug and try to start it.
 

DAMIEN1307

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the rest won't keep it from running.
All the rest of those shortcomings I mentioned in my first post here, combined all together, will indeed keep it from starting and running properly.

Ps...This, of course, is not discounting what you have also added for things to check out as well Chainlube...lol.
 

Chainlube

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All the rest of those shortcomings I mentioned in my first post here, combined all together, will indeed keep it from starting and running properly.

Ps...This, of course, is not discounting what you have also added for things to check out as well Chainlube...lol.
His choke is okay, the arm runs in a line with the flapper, so when lifted it closes, I've had a couple engines like that. The fuel filter being on upside down isn't all that critical, just something to correct. But the real issue is with the mag.
 
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