Small Engines (Lawn Mowers, etc.): Craftsman Garden Tractor, hp briggs, piece of dirt

Question
Hi Michael,
I recently purchased a used Craftsman garden tractor (model#917.273041)from my father-in-law.  It has been in his garage for about a year without being used.  When I went to start it, it ran fine while it was parked in neutral with the brake locked, but as soon as I got on it and engaged the hydrostatic transmission the trouble started.  The engine is a 20 hp Briggs and it sort of revs when driving.  It will go from running full throttle to almost dying and then back again.  It also showed decreased power when going up a hill.  I have drained the gas tank and refueled, with no help.  It also has a new solenoid installed and the battery needs to be  charged, I jumped it to start.  If you have any recommendations I am open to trying them.
Thanks,
Brent  

Answer
Hi Brent,

If the plugs are new, the air filter is clean and the oil level is correct, I would suspect a lack of fuel flow to the engine.  The carb may be gummed up with old fuel or there might be a piece of dirt in the float's needle and seat.  The float might need adjusting also.  First you could try a new governer spring but if no change, a disassembly of the carb or at least the float bowl, may be needed.   If you wish to tackle the carb let me know how you make out and if you need more info.

Michael