Valve Seals / Air Chuck

I like to use a peice of rope in the cylinder instead. No chance of lost pressure, and no compressor needed. Put the piston to TDC on compression, then rotate the crank 90* counter clockwise (backwards) to get the pistons down in the bore. Then slide the rope thru the spark plug hole, and bring the piston back up until it stops. this will hold the valves up so You can work with them. I like clothes line myself..about 2' is more than you'll need. (you dont want to fill the cylinder when it's down in the bore, just fill the space when the piston is at TDC)