Put stabilizer in the tank and run it up to temperature, this get stabilized fuel and the corrosion inhibitors in the fuel system and pump. on a 2 stroke i usually pull the air box off and fog through the carbs until it dies to ensure i get the crank bearings well covered. but in a 4 stroke the air fuel does not go under the crank. so i would pull the plugs and give each cylinder a good shot and then rotate the engine a few cycles with the kill switch off to distribute the oil( i feel that fogging is less important on 4 strokes though so its your choice). replace or check and gap plugs. next, drain the carbs and clean them. change the oil, i favor doing this in the spring opposed to the fall for 3 reasons. 1: to remove any moisture that may have accumulated over the winter. 2: the oil becomes slightly acidic due to combustion gasses and can lose some of its corrosion inhibiting properties. 3: i feel that some of the "grunge" that the oil has picked up over the winter tends to precipitate out and settle in the motor after sitting for a few months.
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