I replaced the spring with the original one and set the lever "by the book". There is no problem running the engine through entire throttle range. Mixture is fine. Still there is a problem of two kinds:

1. From idle slam the throttle wide open and the engine hesitates. Doesn't die but it runs very rough. If I move the throttle slowly (about 1/2 second from idle to WOT) engine accelerates without problem.

2. If I set the idle to quite low but stable then run the engine at WOT for a while. Then I suddenly close the throttle to idle the engine dies. When move throttle slower (about 1/2 sec from WOT to idle) the engine deaccelerates without problem and stays at idle. If the idle is setup higer and I shut down the throttle from WOT the engine doesn't die. Just slows down to the high idle.

Any tips for that?