ORIGINAL: cheesewizz69
Just to add to what Scott posted. If you still can not get the engine to shut down with the throttle closed then either the butterfly is not closing correctly or you have a air leak between the carb and ISO block or ISO block and head.
Also if your engine is too lean it will continue to run fully closed, as some air in the closed position is still allowed to run through. Try 1/8 turn out on the low side and see if it makes a difference.
Cheers, Chris