Just bought a well used Snapper with Kubota WG740 gas engine. It has 1700 hrs, plus some severely deferred maintenance. It starts right up and runs well, although it produces a heavy cloud of oil smoke until it warms up. My problem is that as soon as the governor opens the throttle up under load, it starts to miss and load up, black exhaust smoke.until the deck clears out. Previous owner replaced coil, cap and rotor. It seems that the spark is breaking down under load. I tried closing down the plug gap, but that didn't help. Compression is 150 on all 3 cyl.s. Air filter is not plugged. Looks like #3 is my smoker, swapped plugs around, no change. Seems to miss on all cyls, so I tried a dfferent coil wire. no help.???????????