So, we're cutting back on expenses & I've got to get my wife's lawn mower I've now married into running again. Shouldn't be a big deal since it's a Honda motor & was stored without gas.

HOWEVER, she was under the mistaken belief that the engine needed a gas-oil mixture . . . in place of the 10W30 called for on the big sticker above the fill valve. It sounds like she may have run it that way for a 3-4 years.

The spark plug is fouled, and the oil is too clear on the dipstick & smells of gas.

Other than addressing the spark plug & changing the oil, is there anything else I need to do to or check prior to the 1st mow?

 

Nothing else you can do.
If she mixed oil in the gas it should have just fouled the plug and smoked.
If she used gas and oil in the crank case instead of the oil it should have lock up long ago.

 

There's not much you can do other than change the oil, clean the plug and give it a try. Mowing at full throttle in tall grass will work the engine hard and help burn off or blow out and clean up the cylinder head and valves if she ran oil in the gas.

 

Are you sure she put the gas/oil mixture in the crankcase? Normally when there is gas/oil in the engine, it's because the carburetor is leaking. Often, when people find out there is gas in the oil, they figure someone poured it there by mistake when that isn't the case.