Small Engines (Lawn Mowers, etc.): briggs & stratton carbureator, engine model type, briggs stratton

Question
cranks real easy but the motor surges while running

Answer
Have you cleaned the air filter or carburetor?

http://faqs.custhelp.com/cgi-bin/faqs.cfg/php/enduser/std_adp.php?p_faqid=1874&p...

The most likely problem is a dirty carburetor.  There are several videos on You Tube that show you how to clean carburetors.  

If you want to send me you engine model, type and code number I can look up which carb you have.
Eric