Riding Lawn Mowers

IN APRIL OF 2012 I BOUGHT A HUSQVARNA YTH22V42 TRACTOR. ALMOST IMMEDIATELY I ENCOUNTERED ENGINE START PROBLEMS. WHEN COLD, IT CRANKS AND CRANKS ,BUT IS VERY DIFFICULT TO START.I'VE EVEN RAN DOWN THE BATTERY TRYING. I'VE PUT IN NEW GAS, NEW GAS CAP,NEW PLUGS, NEW FILTER, BUT PROBLEM PERSISTED. SO ONE DAY MY BROTHER AND I DECIDED TO PUMP AIR INTO THE TANK, AND GUESS WHAT... IT STARTS EVERY TIME USING THIS PROCEDURE!PLEASE TELL ME EXACTLY WHAT IS WRONG WITH THE SYSTEM THAT FORCES ME TO GO TO SUCH EXTREMES TO SIMPLE START MY TRACTOR.
THANK YOU, GARY