Small Engines (Lawn Mowers, etc.): craftsman riding lawn mower, craftsman riding lawn mower, speed transaxle

Question
craftsman 16.5 hp electric start 42" mower, 6 speed transaxle lawn tractor (model #944.605320).  pull hair surging, new carb, new fuel pump, new fuel line, new filter, still surging.  Timing belt is vertical crank.  any suggestions to fix surging.  not a lot of holes to change govenor spring setting.  should i make it stronger or weaker in spring tension or leave as is.

Answer
Do you have fresh fuel?  Take a remote fuel tank and get fuel from that tank.  lets rule out fuel pump, fuel line obstructions, etc.  Sometime the only way extreme surging can be resolved is by changing the gov gear inside of the engine... there is a chance it may be bad.