Small Engines (Lawn Mowers, etc.): Toro S-620, air mixture, exhaust valve

Question
Have a Toro S-620 mod 38162 eng AH-600 type 1623-A.
Difficult to start, once started dies shortly unless I hold my hand directly over the air intake of the carb. At this point it run rich but runs. Any suggestions.  Thanks

Answer
Most likely is that you have a restricted jet in the carburetor.  I would start by taking the carburetor apart and cleaning the jets and passage ways out with spray carburetor cleaner and compressed air.  Also an exhaust valve that is out of adjustment can give the appearance of a carburetor problem by drawing air in through the improperly seated exhaust valve and changing the fuel to air mixture.  This condition is most effectively diagnosed by the use of a cylinder leakdown tester. Most likely though is that you have a restricted jet in your carburetor.