1. Drain and flush the cooling system. I made the mistake of not flushing out the cooling system on my S2 after it had been sitting for several years. I saw no rust particles in the drain pan so made the bad assumption that the system was clean. Bad mistake. I spent years chasing down a cooling issue that a radiator back flush finally fixed.
2. Turn the motor over by hand, make sure nothing internally is frozen. I see no need to replace the head gasket at this time.
3. Drain the gas tank and add fresh gas.
4. Prime the oil pump and change the oil.
5. Disassemble the Strombergs and blow out all passages with carb cleaner and compressed air. Make sure that the air valve diaphragm is not rotted and operates smoothly
6. Keep fingers crossed, first start up is always stressful.