#1 never prime an engine that you are going to use a starter on #2 if using an electric fuel pump always disconnect the muffler pressure line to avoid filling the muffler and engine with fuel, if you are worried about spilling fuel get a small fuel tank that you can connect to the muffler pressure line as an overflow tank. If this is a brand new engine that you are breaking in on the bench i would get rid of the spinner and just use the nut, also heating the engine a bit with a heat gun can aid in starting a new engine.