RC Model Reviews

The nipple on the crankcase is for hooking up an external fuel pump. It creates a vacuum pulse that operates a diaphragm type fuel pump, If you dont use it for this purpose you must cap it off or yo will lose crank case pressure. The nipple on the exhaust is intended for fuel tank pressure but im not sure your 4 stroke will need this. If you find it leaning out when you hold your plane vertical then you sold try hooking this line up to your fuel tank