Small Engines (Lawn Mowers, etc.): B&S wont take load, fuel tank cap, vacuum leak

Question
12F702-0816 on a John Deere 14PZ push mower, about 12 years old.  I was having problems starting it and keeping it running (would shut down and would only restart after priming).  Rebuilt carb, replaced gas, tried to make sure all linkages were straight.  Engine now runs, but seems to surge when unloaded, and will bog right down and stall when loaded.  The governor linkages are all intact but it doesn't seem to be able to adjust for loading any more.

The carb is the priming type, and there is no gas filter.

Answer
Mike
Sounds like your Problem may be that Engine lacks power (possibly after warmup).
Possible causes:

Old gas, bad spark plug, very thick/dirty oil.
Choke is partially closed.
Carburetor needs adjustment or service.
Ignition not timed correctly.
Air filter is clogged.
There is a lack of lubrication.
Valves are not sealing properly.
Piston rings are not sealing properly.
Head loose or head gasket blown or damaged.

and if the Engine operates erratically, surges, and runs unevenly.
Possible causes:

Fuel line or fuel tank cap vent is clogged.
There is water in the fuel.
Fuel pump is defective.
Governor is not set properly, sticking, or binding.
Carburetor needs adjustment or service.
Loose carburetor/intake pipe resulting in vacuum leak.