6. CYLINDER HEAD/VALVES STRYKER 125/150 Tap the valve stems gently with a plastic hammer for 23 times to firmly seat the Plastic Hammer cotters. Be careful not to damage the valves. CYLINDER HEAD INSTALLATION Gasket Install the dowel pins and a new cylinder head gasket. Install the cam chain guide. Dowel Pins Cam Chain Guide Install the cylinder head. Cylinder head 6-15