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Discussion Starter · #1 ·
Recently got a cheapy 49cc pocket bike with a cracked engine replaced engine everything runs and drives but it seems to not get enough fuel? Low idle/very little power, as well as sputtering out after throttle? Tried adjusting fuel mix screw with no luck not sure where to go from here, carb is brand new as well
 

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What's your poison? Mine is 40:1
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Welcome, so you bought a brand new engine?? Did you pull it apart to look it over?? There might have been metal shavings in the engine. I would pull the carb and check/clean it. Make sure it is flawless.
 

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Discussion Starter · #4 ·
I checked it before installing, cylinder is clean and piston is fine, good compression as well
Correction as well engine was cracked along the fly wheel and rubbing and that's what I thought was causing the problem, I did tear down and clean the carb tho as it's easy but I don't know much about the engine so kind of scared to go farther than inspecting cylinder wall and piston etc
 

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Correction as well engine was cracked along the fly wheel and rubbing and that's what I thought was causing the problem, I did tear down and clean the carb tho as it's easy but I don't know much about the engine so kind of scared to go farther than inspecting cylinder wall and piston etc
If your engine has good compression, spark, fuel, and the carb and cylinder is clean, I would check one more thing: Did your new engine come with a brand new muffler, or did you put an old one on it? If you are using an old muffler, then if it has a spark arrester screen on it make sure its not clogged with carbon, and if it doesn't have a spark arrester, make sure the muffler isn't full of carbon and unburned 2-stroke oil. I have and APC mini chopper I have been restoring and I had this problem. Everything else was good, the carb was new, it had spark and compression, It just couldn't get the exhaust out fast enough with the clogged muffler. I replaced the old muffler and it ran great.
 

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Discussion Starter · #7 ·
If your engine has good compression, spark, fuel, and the carb and cylinder is clean, I would check one more thing: Did your new engine come with a brand new muffler, or did you put an old one on it? If you are using an old muffler, then if it has a spark arrester screen on it make sure its not clogged with carbon, and if it doesn't have a spark arrester, make sure the muffler isn't full of carbon and unburned 2-stroke oil. I have and APC mini chopper I have been restoring and I had this problem. Everything else was good, the carb was new, it had spark and compression, It just couldn't get the exhaust out fast enough with the clogged muffler. I replaced the old muffler and it ran great.
Currently no exhaust on it
 

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Ok, do you have the horizontal engine, or the vertical engine. You'll need to put the exhaust back on it to get things running correctly. Try setting your fuel screw back to it's normal position, if you remember what it was, then adjust the idle first. Once the idle is correct, do a few pulls on the bike (just ride it up and down the street a couple times), and see what's going on. If the bike is revving up fairly quickly, but not really moving, it's your clutch slipping. If the engine seems to be doing what it's supposed to, but down on power, then adjust the fuel screw.
 

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Discussion Starter · #13 ·
Ok, do you have the horizontal engine, or the vertical engine. You'll need to put the exhaust back on it to get things running correctly. Try setting your fuel screw back to it's normal position, if you remember what it was, then adjust the idle first. Once the idle is correct, do a few pulls on the bike (just ride it up and down the street a couple times), and see what's going on. If the bike is revving up fairly quickly, but not really moving, it's your clutch slipping. If the engine seems to be doing what it's supposed to, but down on power, then adjust the fuel screw.
Vertical, there isnt a place to put an exhaust muffler on its just a very short pipe coming out the engine and to the side, clutch should be fine its brand new? It idles fine just cant rip it cuz it sputters out and cant start it again till i reprime the carb
 

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Vertical, there isnt a place to put an exhaust muffler on its just a very short pipe coming out the engine and to the side, clutch should be fine its brand new? It idles fine just cant rip it cuz it sputters out and cant start it again till i reprime the carb
The vertical engines should have a little box shaped exhaust like lawnmowers, leaf blowers, trimmers, and the like. I believe your exhaust is already installed. You also stated that it has a weird/ weak idle. That's why I started at that point. Also, referring to re-priming the carb...

Just realized one of my fuel lines is very hard like old maybe and not an airtight seal to the gas tank is that a problem?
Do you have bubbles in the line when you prime the carb? You've probably already found your culprit, and you're just getting air in the lines, and running out of fuel.
 

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Discussion Starter · #16 ·
The vertical engines should have a little box shaped exhaust like lawnmowers, leaf blowers, trimmers, and the like. I believe your exhaust is already installed. You also states that it has a weird/ weak idle. That's why I started at that point. Also, referring to re-priming the carb...



Do you have bubbles in the line when you prime the carb? You've probably already found your culprit, and you're just getting air in the lines, and running out or fuel.
When i prime it im not getting any air in the lines but i think the little primer bubble has no gas left only air when it sputters out but i didnt see air in the line?
 

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can you sent a picture of your setup? Pictures from the carb all the way to the tank? It seems like something is either slowing fuel to the carb, or the carb itself isn't assembled tightly enough, and is having a vacuum leak.
 

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Discussion Starter · #18 ·
can you sent a picture of your setup? Pictures from the carb all the way to the tank? It seems like something is either slowing fuel to the carb, or the carb itself isn't assembled tightly enough, and is having a vacuum leak.
Sure i get home around 230 but heres the engine and carb setup, fuel lines run down from a tank above then engine,
 

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Sure i get home around 230 but heres the engine and carb setup, fuel lines run down from a tank above then engine,
I have that exact same engine on my APC Mini Chopper that I restored. If the fuel lines are old and hard definitely replace them. You also said there is no fuel in the primer bulb so, make sure that is not cracked. Like Falkon45 said, make sure that the carb is assembled tightly enough otherwise you might have a vacuum leak. Also make sure the gasket that goes between the carb and the engine is still good, or you could have an air leak there.

In regards to the fuel flow problem, if the carb and the lines are still good, make sure the fuel filter isn't clogged up with dirt/debris since I would imagine that the fuel flow could be slowed if it is clogged.

Also, is your carb new?
 

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Discussion Starter · #20 ·
I have that exact same engine on my APC Mini Chopper that I restored. If the fuel lines are old and hard definitely replace them. You also said there is no fuel in the primer bulb so, make sure that is not cracked. Like Falkon45 said, make sure that the carb is assembled tightly enough otherwise you might have a vacuum leak. Also make sure the gasket that goes between the carb and the engine is still good, or you could have an air leak there.

In regards to the fuel flow problem, if the carb and the lines are still good, make sure the fuel filter isn't clogged up with dirt/debris since I would imagine that the fuel flow could be slowed if it is clogged.

Also, is your carb new?
Carb and engine both brand-new, I have the old carb as well too that I cleaned myself that I could try but I don't think that would be the problem?
 
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