Ok so I purchased a motor kit about 1 year ago, I have recently been getting back into motorized biking. Ok so heres the probelm. I always have to have it set at half choke while I am riding it, if I turn the choke a little less then half and give it gas it will start to make a relly loud knocking noise and if I turn the choke all the way off and give it gas it will lose all power and stall. Im buying a boost bottle becuase ive herd they help with idle. Ive checked everything im guessing that I could not be getting enough gas or its not getting enough air if you know what could be wrong and can help that would be awesome thanks!
Problem with 2 stroke motor
- Thread starter Hunterlee99
- Start date
Hunter that's a strange malfunction you have there.
With the choke on it will suck a bunch of gas but less air. Maybe your carb needs cleaned and adjusted. Assuming it's a China girl with an NT, you could check the main jet for a clog and set the float height. Then again, it may have an intake vacuum leak at the carb/manifold joint, the manifold/cylinder joint, or even the main seals.
Since it's new, it's likely the seals are fine. It's sucking in illegal air to run, or needing to draw extra hard on the jet to get gas. It's hard to say from here, but I'd clean and adjust the carb first, then make sure the manifold's mating surface is flat and the gasket is good. Put a thin coat of gasket goop on it and torque the nuts down equally. Make sure the carb is seated all the way on the manifold and hold it there as you tighten the clamp.
Hope ya get it sorted out.
With the choke on it will suck a bunch of gas but less air. Maybe your carb needs cleaned and adjusted. Assuming it's a China girl with an NT, you could check the main jet for a clog and set the float height. Then again, it may have an intake vacuum leak at the carb/manifold joint, the manifold/cylinder joint, or even the main seals.
Since it's new, it's likely the seals are fine. It's sucking in illegal air to run, or needing to draw extra hard on the jet to get gas. It's hard to say from here, but I'd clean and adjust the carb first, then make sure the manifold's mating surface is flat and the gasket is good. Put a thin coat of gasket goop on it and torque the nuts down equally. Make sure the carb is seated all the way on the manifold and hold it there as you tighten the clamp.
Hope ya get it sorted out.
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I have never tried a boost bottle because the small size of the nipples and line wouldn't (in my opinion) move enough air to make a real difference and it could be another source of intake leaks and tuning weirdness. I like to keep things as simple as possible, and value reliability over speed or looks.
The bike should idle and run fine without a boost bottle or else something is wrong, ya know?
The bike should idle and run fine without a boost bottle or else something is wrong, ya know?
Ok I will have to try some new things tomorrow. Thank you so much I will get back here tomorrow and let you know how things are going
It alsoi sounds to me like your carb is the culprit, especially if it's been sitting for any length of time the gas inside the carb will gum everything up. It's pretty easy to remove the carb then remove the float bowl, get a can of carb & choke cleaner and a set of welding tip cleaners to get into the small passages and ensure nothing's blocked off or obstructed. Use the carb and choke spray to dissolve and blast away any gunk that don't belong in there. You want to make sure there's no obstructions at the needle and seat valve, the main jet, and the atomizer. The atomizer is usually not an issue since the main needle goes thru it, but if it has any buildup on the needle or in the tube it could cause the fuel to go into the engine as larger droplets than a fine mist, making cold starts and warmup a real pain.
Also check your head gasket, mainly be sure the nuts on top of the head didn't come loose, this will make the engine very hard to start and perform very poorly if you have even the slightest compression leak.
Check that you have no air leaks at the carb to manifold, the manifold to cylinder, the cylinder base to case, and the case split line. There's also the crank seals, but they can usually survive the typical sitting for several months scenario, but be willing to check there too if all else looks good. As a last resort, take the head off and inspect your piston crown and cylinder wall for any abnormalities. Do a compression check if you have a compression tester as well, compression should be around 100psi on a stock engine, and 130 to 160 with a high performance head installed.
Another thing to consider if the carb is really bad is replacing it since the stock carb usually costs under $15 and it can be cheaper than trying to fix.
Another place that gets overlooked is the exhaust, if you got the stock exhaust, you can check it by removing the end cap and make sure there's nothing in there that's not supposed to be like mud daubers nests etc...
Also check your head gasket, mainly be sure the nuts on top of the head didn't come loose, this will make the engine very hard to start and perform very poorly if you have even the slightest compression leak.
Check that you have no air leaks at the carb to manifold, the manifold to cylinder, the cylinder base to case, and the case split line. There's also the crank seals, but they can usually survive the typical sitting for several months scenario, but be willing to check there too if all else looks good. As a last resort, take the head off and inspect your piston crown and cylinder wall for any abnormalities. Do a compression check if you have a compression tester as well, compression should be around 100psi on a stock engine, and 130 to 160 with a high performance head installed.
Another thing to consider if the carb is really bad is replacing it since the stock carb usually costs under $15 and it can be cheaper than trying to fix.
Another place that gets overlooked is the exhaust, if you got the stock exhaust, you can check it by removing the end cap and make sure there's nothing in there that's not supposed to be like mud daubers nests etc...
Davezilla i dont think that could be the probelm bebecause I turn the gas from the tank off (I think its called the pitcock or something like that) but I will pull it out and clean it anyways thanks
Yup... it's either not enough fuel or too much air, if it ran ok before then I'd say too much air and to check for the typical air leaks at the intake and where the carb slips over the intake,(check these anyway, it's still very possible that's it) but if it's always been a problem from day 1, then that's where i say check everything, it's very possible that you're one of the many that got a free bonus inside your gas tank, they like to include metal shavings, pieces of newspaper, and all kinds of other tiny debris in the tanks that can go down and clog filters, jets, and anything else that may ensure a good running engine... Check everything but start with the easy stuff first and work your way up...
I was never able to take it off full choke I am going to try to drill out a few holes in my air filter would that be fine?
Once you get your engine working right, sure.
I always umm, relieve my air cleaner covers.
Since you have to keep the choke part way on to run, doing it now would only make it worse. Even more air to choke off..
Not yet... If you've always needed some choke to it then you're getting too much air already... but this extra air is coming from either a leak at the carb to intake manifold connection, the manifold to the cylinder gasket, or your carb may be partially blocked off on the fuel side making the problem more like not enough fuel than too much air...
are you using a fuel filter? and have you always used one?
Did you clean out the gas tank Really good before installing and using it? The chinese love to leave these little gifts of paint chips, paper particles, metal shavings, and other junk in there, all this can clog up the filter that's inside the tank at the petcock, if you remove the petcock you will see this filter... if it's clogged up with junk it can be cleaned and reused, but it's by no means good enough to block that junk from getting down into the carb.
Personally I just discard that in tank filter and run a see thru inline filter so I can see when it needs to be changed, they cost like $3 at most auto parts stores.
If you got good fuel flow from the tank... you can check by removing the fuel line from the carb and opening up the petcock and letting it drain into a gas container, if the flow looks restricted and not steady, it's most likely that filter starving the engine.
If that part flows good, then it's time to look at the carb, small particles of who knows what can block off or partially block off the float needle and seat valve or the main jet which would also make you need to partially choke the engine to keep it running.
The easy things to check are the carb and intake for air leaks, you can start the engine then spray a little carb cleaner, just a short blast at the intake right at the cylinder, listen to the engine, it may even kill the engine if the spray hits a leak, or it could rev the engine either way, you'll know there's a leak there... also check the base of the carb where it connects to the intake manifold for similar results.. any change in the engine means a leak.
If both these pass, then spray at the cylinder base, and the case's split line as far as you can reach, Case leaks are uncommon but I've seen one or 2.
The toughest leaks to detect are at the crank seals, but you can run the engine with the mag and clutch covers off, spray the carb cleaner as close to these seals as possible and listen for a change in the engine.
That'll help you find any air leaks...
The air leak checks are easy, but the fuel restriction checks aren't that difficult, I always check the easy stuff first, but mine was fuel starving due to the NT speed carb's fuel valve shedding off rubber particles into my needle and seat valve and main jet, the bike would run perfect but hit a wall at around 20mph and refuse to go any faster, and then if I stayed on the throttle it would begin to sputter and act like it was going to die. Once I found the problem and cleaned all the mess out it ran fine.. for about a day and did it again, at that point I gutted out the built in fuel valve at the carb and never had another problem but I finally ended up putting on a regular NT carb once everything was cleaned up again and it never ran better.
are you using a fuel filter? and have you always used one?
Did you clean out the gas tank Really good before installing and using it? The chinese love to leave these little gifts of paint chips, paper particles, metal shavings, and other junk in there, all this can clog up the filter that's inside the tank at the petcock, if you remove the petcock you will see this filter... if it's clogged up with junk it can be cleaned and reused, but it's by no means good enough to block that junk from getting down into the carb.
Personally I just discard that in tank filter and run a see thru inline filter so I can see when it needs to be changed, they cost like $3 at most auto parts stores.
If you got good fuel flow from the tank... you can check by removing the fuel line from the carb and opening up the petcock and letting it drain into a gas container, if the flow looks restricted and not steady, it's most likely that filter starving the engine.
If that part flows good, then it's time to look at the carb, small particles of who knows what can block off or partially block off the float needle and seat valve or the main jet which would also make you need to partially choke the engine to keep it running.
The easy things to check are the carb and intake for air leaks, you can start the engine then spray a little carb cleaner, just a short blast at the intake right at the cylinder, listen to the engine, it may even kill the engine if the spray hits a leak, or it could rev the engine either way, you'll know there's a leak there... also check the base of the carb where it connects to the intake manifold for similar results.. any change in the engine means a leak.
If both these pass, then spray at the cylinder base, and the case's split line as far as you can reach, Case leaks are uncommon but I've seen one or 2.
The toughest leaks to detect are at the crank seals, but you can run the engine with the mag and clutch covers off, spray the carb cleaner as close to these seals as possible and listen for a change in the engine.
That'll help you find any air leaks...
The air leak checks are easy, but the fuel restriction checks aren't that difficult, I always check the easy stuff first, but mine was fuel starving due to the NT speed carb's fuel valve shedding off rubber particles into my needle and seat valve and main jet, the bike would run perfect but hit a wall at around 20mph and refuse to go any faster, and then if I stayed on the throttle it would begin to sputter and act like it was going to die. Once I found the problem and cleaned all the mess out it ran fine.. for about a day and did it again, at that point I gutted out the built in fuel valve at the carb and never had another problem but I finally ended up putting on a regular NT carb once everything was cleaned up again and it never ran better.
Now I lost the idle screw today
does anybody know where I can order one? Or would an old weed eater idle screw work?
does anybody know where I can order one? Or would an old weed eater idle screw work?In a pinch they might have a screw at the hardware that works. Bring the carb with you and see if there's a metric machine screw that will thread in there.
If so, buy it and a nut that fits it.
Taper the tip like the original was on a grinder (or dremel it) being careful not to booger the threads, then set the idle and tighten the nut like a lock to keep it there.
When you locate a real one, change it out. Or don't, because you fixed it.
You can get an NT for $15 so there aren't many vendors selling parts for them.
I could be wrong, though.
Good luck!
If so, buy it and a nut that fits it.
Taper the tip like the original was on a grinder (or dremel it) being careful not to booger the threads, then set the idle and tighten the nut like a lock to keep it there.
When you locate a real one, change it out. Or don't, because you fixed it.
You can get an NT for $15 so there aren't many vendors selling parts for them.
I could be wrong, though.
Good luck!
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I agree... just take the carb with you to home depot or lowe's and you should be able to find one that fits... not sure what type of tooling you got, but a dremel or any small grinder will make short work out of tapering the end threads
