idle and starting problems

[50cckeeway]

Got a 50cc 2 stoke. Starts right up after having the carb cleaned but dies when I start to throttle. If i rev it in short bursts a for a minute or two eventually something changes and very suddenly it fires up like normal.
Not trying to start it cold. This is after letting it warm up at idle for a few minutes.
A friend said it sounds like the throttle is sticking. And/or that it's running too rich. I was also told it's running too rich when i changed the spark plug and the old one came out black and sooty.

Where would I look for the choke and how would i adjust the mix to make it more lean?

[jtl]

I can only tell you about my scooter but the air/fuel mix should be a small screw just below the idle screw which is usually larger and often has a spring on the screw. On my carb if you turn the screw clockwise (in) it will run more rich, cc (out) for more lean. I have mine set at about 1 1/2 turns out, but you can experiment with this. Can't tell you anything about the choke.

[90GTVert]

I'd start by adjusting the mixture as jtl described and see if that gets you anywhere. That's only the idle mixture, and won't affect much else. To you can move the clip on the jet needle in the carb to lean it out some in the midrange. You'd need to swap the main jet to lean out the upper end of the throttle.

The choke, or automatic enrichener, will probably look like a black cylinder on the side of the carb.