Craftsman 21.5 HP Intek loss of power
It has 407 hrs. on the motor. It started to lose power while mowing. I immediately shut it off and checked the oil. Not much. I filled it up with oil and cleaned the air filter. The motor will run fine under no load. Once the blade is engaged it runs strong momentarily and the bogs down to failure/off if I let it.
One plug was sooty. No oil on the plugs.
I've never changed the fuel filter.
Do you have any ideas?