Allways use new gaskets when you reassemble an engine and donot substitute silicoln or engine sealer in place of the cylinder base gasket as you will change the port timing of the motor the only place you use an engine sealer is when you split the crankcase to take the crank out then you will need a crankcase sealer polaris shop should have this on hand do not use rtv in place of this as it will attack the aluminum case and arrode away at it wich will make the case useless.