Thread: uneven power
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Old 09-01-2015, 06:47 PM
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Agreen Agreen is offline
Motorized Bicycle Elite Member
Join Date: Feb 2013
Location: Goose Creek, SC
Posts: 624
Default Re: uneven power

The coiled up ignition wire is not helping. I won't say that it's the problem, but it should be straight to prevent it from losing power to a magnetic field.

The standard NT carb can not be adjusted without changing the jets. They are, however, incredibly easy to change out. I had an old broken carb that I stole the jet from and started by soldering the jet shut and drilling it to a smaller size. Turned out, I needed a larger jet because it made far less power. When I went down in jet size, it felt like the throttle was closing some when I opened it past 3/4. It just bogged down and got more quiet. That meant it was lean. I went to a larger jet then, and WOW what a difference it makes! If you go too rich, the engine will also lose power, but it'll braap at you a lot. Instead of it making the normal 2 stroke noise, the frequency gets cut in half, thus the term 4 stroking.

The needle setting depends on the size of the main jet. Before I changed the jet, it was happy at the 2nd from the top notch. The needle controls everything upnto 3/4 throttle. After I drilled the jet larger, I had great WOT power, but partial throttle was 4 stroking. I raised the clip all the way up (which leaned it out) and the normal power returned. The main jet changes the fuel flow to the throat of the carb, the needle restricts it below 3/4 throttle.

Having the extra jet made swapping them out way easier. It minimized the amount of time the carb was apart, which helps keep dirt and debris out.

If you need to go to a smaller jet, soldering the hole shut can be accomplished a couple different ways. I used a plumber's torch and electrical solder. I soldered on the non-threaded side, and just a LITTLE dab is all you need. Otherwise you'll be drilling it out a lot. And only keep the jet in the heat for about 5 seconds. Anything more and you'll melt the jet. Some people use a soldering gun and plumber's solder with brush in flux. It doesn't matter, so long as you solder it right and don't make globs.

The tiny drills are the hardest part. I was so afraid I'd break one that I drilled for like 30 minutes before I grew a pair and put pressure on it. They do break easily, but they aren't made of glass.

Last edited by Agreen; 09-01-2015 at 06:55 PM.
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