Make sure fuel cut-off switch is in the "open" position, change fuel filter, drain old fuel and add fresh fuel with Seafoam added to clean fuel system. Old fuel that has not had stabilizer added to it when it was fresh becomes varnish and gums up the fuel system. Is the fuel old or has it been in there a while? Try these first and see if this cures the problem.
Toro Wheel Horse 522xi GT, Honda HS928TA, Honda HS621AS, Honda HS520A, Toro CCR3000 (work in progress), Honda HS624WA (sold 08/23/2010), Stihl BR550 Backpack Blower, Stihl MS250, McCulloch MS1635, Honda EM6500SX Generator