Small Engines (Lawn Mowers, etc.): Engine Pulsates, carburetor, yard sale

Question
I recently picked up a Toro GTS self propelled at a yard sale.  Wouldn't start.  It had been sitting awhile from the looks of the carb.  I cleaned the carb out, replaced the plug, changed the oil and cleaned the air cleaner.  It started right up however, the engine pulsates while running.  What did I miss?

Answer
Most of the pulsating is caused by the carburetor.  I would check all the gaskets associated with the fuel system to make sure none of them are leaking.

Secondly, I would pull the carburetor apart and clean again...I have had a couple of carbs that I have had to clean multiple times.

Finally, you would have a weak governor spring or the RPM is not correctly set.  Some engine governors are more sensative than others.  You will need a tachometer to check the RPM...should be 3600 RPM.

Let me know what you find.  I'm always interested in surgining problems since most of them turn out to be carb problems.
Eric