Small Engines (Lawn Mowers, etc.): mower runs but stalls, kohler command, hydrostatic transmission

Question
I have a JD Sabre 2354 with a Kohler Command 23 HP V-Twin with automatic/ hydrostatic transmission.  My mower will start up and run fine with the parking brake on.  As long as the parking brake is on it will continue to run fine as long as I want but if the parking brake is released or the PTO is engaged the engine stalls.

Answer
HI  TIM

SOUNDS LIKE   SEAT SWITCH PLAYING UP  HAVE YOU CHECKED THAT SEAT SWITCH IS OPENING
 ( TRY PULLING THE WIRES FROM SEAT SWITCH AND RETESTING

SOUND LIKE A OPERATOR PRESENCE PROBLEM  ( THE LACK OF )  THIS SWITCH SHOULD BE OPEN WHEN YOU SIT ON IT  AND BE CLOSED WHEN YOU GET OFF IT  (GROUNDING THE IGNITION COIL PRIMARY TO EARTH)

AS ANOTHER TEST TRY  CONNECTING THOSE WIRES WITH A JUMP WIRE  

PARK / BRAKE SWITCH  HAS NOT STUCK DOWN HAS IT ?

IS THE UNIT IN NUETRAL AND NUETRAL SWITCH HAS NOT STUCK ?


DOES ENGINE RUN AND REV FINE WITH BRAKE ON - IF SO NOT ENGINE POWER PROBLEM


IF SO SO THEN ITS DEFINATLY  INTERLOC SAFTY SWITCH PROBLEM  

DOES UNIT HAVE A REVERSE IMPLEMENT SWITCH   ( RIS ) BUTTON ( THIS IS ONE YOU NEED TO HOLD IN WHILE YOU MOW IN REVERSE  WITH BLADES GOING )  HAS THIS STUCK ON / IN  ?

HAVE A LOOK AND LET ME KNOW WHAT YOU FIND  

CHEERS PAUL