Hi, all.
i've got a problem with the engine.
that is running well on high rpm, but can not adjust idle rpm, right after i close throttle to minimal rpm it stops after 2 sec.
What do You think are the reasons for that.

Listen to the engine carefully. Quitting after a second or two usually means that you're either trying to close the carburetor too much, or the idle mixture's much too lean.

At idle, the carb will still be open about 1/16" or so, but maybe a bit more or less.

To check the idle mixture, back out the idle mixture screw one turn. Start the enigne and reset the high-speed needle valve at full throttle. Then retard the throttle slowly and adjust the idle mixture as necessary, it should be quite rich.. You should eventually find a good RPM and mixture setting.

Refer to the instructions to get the idle mixture 'ball parked' at a starting setting if it's 'way out of whack.

Thanks for advise, i think it may be some dirt in carb, so i'll clean it up in just of case. What do You, think, what is the bes rpm for idle

There is no "best" idle RPM. Anything below 2,300-2,400 RPM with a good acceleration would be considered acceptable. Lower is gravy. Just make sure the engine will accelerate after about 30 seconds (at least) of idling.

A well-broken-in and set-up engine can idle almost indefinitely and still accelerate to full.