Small Engines (Lawn Mowers, etc.): oil pump govenor, conrod, rideon

Question
My friend has a 11.5hp motor on his rideon and it has done the conrod well shattered it I've put a new conrod in and the mower is surging when you start it there is nothing wrong with the valves and crank all good did not touch the carby just removed sump & head replaced conrod my friend did move the oil pump leaver has it got a place to be set at or is it something else that may be causing the problem

Answer
Most surging is caused by dirty or mis-adjusted carburetors.  What is the eninge model, type and code number so I can look up the parts list.

Read the following info before messing with the governor.

http://www.smallenginesuppliers.com/shop/html/governor_adjustment.html

Eric