7. CYLINDER HEAD/VALVES PEOPLE 125/150 O-ring Apply engine oil to a new O-ring and install it. Tighten the cam chain tension cap screw. Be sure to install the O-ring into the groove properly. Cylinder Head Cover Install a new cylinder head cover gasket and install the cylinder head cover. Install and tighten the cylinder head cover bolts. Be sure to install the gasket into the groove properly. 7-12