making my chopper faster(hopefully)

[syllent81]

to start im new to both this site and gokarts/minibikrs but im trying to learn. about a week ago i found a mini chopper tat was going to be thrown away. it works and runs good but now i want it to be faster. i think it goes 20 mph if not less. its a 2 cycle engine. i attached a picture of it color coded. i tried adjusting those screws(in red) to change the speed but got no real result. i am not sure i am doing it right. i lossened the bottom one most of the way but got better results when it was screwd in a little more. also the lever (in blue) im not sure wat its for. i see tat i can start the bike when its at the top. and when i want to go i simply put it halfway down and pull the throttle to keep it from going off and slowly keep pushing it down to keep accelerating but wen i push it all the way down the bike starts to stutter and wants turns off within about 5 sec if i do not pull the lever up a bit. any ideas would be great.

 

[anderkart]

Screw #1 looks like its just meant to hold the air cleaner on.

Screw #2 looks to be either an idle or main jet adjustment and it sounds like you've tried every possible adjustment posibility.

The lever (circled in blue) is most likely your choke. Normally after an engine is warmed up a bit, the engine will run best with the choke fully opened. The fact that yours runs beter with the choke part way on tells us the engine is running lean. (=not enough gas/too much air) So restricting the incoming air helps to somewhat corect the situation.

There's lots of things that can cause this, some things you could check/try are:

First make sure your gas/oil premix is fresh. (gasoline starts to go bad after about a month or so and can sometimes cause these types of problems)

Make sure your carb isn't just loose where it bolts to the engine. (If its somehow sucking in air here you'll get symptoms just like your experiencing)

There may be a second carburetor adjustment screw hidden somewhere you havent tried adjusting yet.

Your carb might have some dirt inside restricting the normal fuel flow or even defective gaskets/diaphragms causing these symptoms.

You might even have a restricted fuel delivery to the carb issue.

If your engine origanaly had a foam or paper air cleaner element, it may need this in place to run right. (I've seen some small engines jetted so lean they actualy ran better with the filter element instaled.

Or it could be some other problem I didnt think of yet.