21hp Kohler on Z121 Kubota zero turn, Runs well for 15 to 20 minutes, Then starts to sputter like it's running out of gas, tank is full, new fuel filter with flow in the proper direction, fuel pump is pumping fuel. I haven't got in to the carb yet , Hoping I didn't have to go there, any Ideas of problem, also Solenoid is acting up needs replaced ,They are not dependent on each other are they( never heard of that but). Thanks