If an engine runs on choke only, then it is still a fuel system problem. It could be a fuel pump....if your unit has a fuel pump. But it is usually the carburetor that is restricted. I know you said the carburetor was overhauled but it still acts like carburetor. You may have to re cleacn the carburetor and use a complete carburetor repair kit. Another possibility is that the fuel CAP may not be venting. Try running it with the fuel cap loosened . if it does better, then replace the cap with a new one.
Hi,ranwell, thanks for your responce, i had already tried everything you suggested .as a last resort i adjusted the valve clearances which seems to have resolved the problem.