I have a gravely 460 w the kaw fx850v. Mower lost power and quit. Would only run w choke at about 3/4 closed. Replaced fuel lines, fuel filter, pump, fuel solenoid, and now coils. Runs a little better, but the biggest improvement came when I cleaned the surface of the flywheel magnets with emery cloth. I'm guessing the rusted up after I hosed it off. Ive cleaned the carb once, and it runs no different. Any other ideas out there. Mower only has about 185 hrs. Oh and I adjusted the valves. I'm left thinking its a valve issue or maybe a carb issue. At idle engine sounds fine but as I slowly increase throttle, at about 1/2 throttle you can start to hear a sputter... and at high idle it back fires a lot.