Breather valves or pressure relief valves prevent air pressure from building up in combustion engines. They also prevent dust, water and sand from entering the engine crankcase. Breather valves allow the gases from the internal combustion engine to safely be removed from the crankcase. A positive crankcase ventilation system (PCV) contains a variable restriction breather valve called a PCV valve. It reacts to the fluctuations of gas pressure that occur while the engine is running and allows the gas to escape.
Disconnect the negative terminal of the battery. Remove the spark plugs. Remove the air cleaner and air cleaner backing. Remove the ignition cover. Loosen the foot peg or brake pedal. Remove the engine cover and the push-rod tubes.
Remove the cam cover, camshaft assembly, cam support plate and oil pump.
Place the O-ring over the top edge of the crankcase bearing bore. Seat the O-ring into the groove as you press it into place. Insert the breather valve assembly on the pinion shaft of the the crankcase pinion bearing bore. Rock the O-ring to help it move. Gently push the breather valve into the crankcase bearing bore. Stop when the back of the valve housing is sitting on the outer edge of the pinion bearing.
Place the wave spring into the counter-bore of the breather valve assembly. Apply a generous amount of wheel bearing grease to the wave spring. Hold the wave spring into position while you put in the oil pump. Re-install the cam support plate, camshaft assembly and cam cover. Do not force the parts back into place, but firmly push them back in. There will be resistance when reinstalling the cam plate due to the parts pushing down the spring and compressing it, which is normal.
