4 stroke engines have always had the problem where squirting oil into the intake or exhaust only oils the top end of the piston and cylinder. It doesn't do anything to oil the bottom end or the valve train. You might be able to squirt some oil into the crankcase vent, if you have one on the back of the engine, but even then the valve train is still not oiled, so you have to remove the valve covers and oil the top end part, but also dribble oil down the push rod tubes to get to the lifers too. But still the camshaft may not be oiled and protected. If you are going to store the engine, I suggest removing the backplate and valve covers and liberally flushing out the engine good and then oiling it up good. You want to remove as much of the old combustion products residue inside the crankcase as you can before you put it away.