All models are equipped with a Positive Crankcase Ventilation (PCV) system which draws air into the engine through the air cleaner and circulates it through the engine. The air combines with vapors in the crankcase and exits the engine through a metering valve mounted in the rocker arm cover. The air vapor mixture then re-enters the engine through the carburetor or intake manifold and passes into the combustion chambers where it is burned.
- See if there are any deposits in the carburetor passages, the oil filler cap, or the hoses. Clean these as required.
- Connect a tachometer to the engine.
- With the engine idling, remove the PCV valve.
If the valve and the hoses are not clogged-up, there should be a hissing sound.
- Check the tachometer reading. Place a finger over the valve or hose opening (a suction should be felt).
- Check the tachometer again. The engine speed should have dropped at least 50 rpm. It should return to normal when the finger is removed from the opening.
- If the engine does not change speed or if the change is less then 50 rpm, the hose is clogged or the valve is defective. Check the hose first. If the hose is not clogged replace, do not attempt to repair, the PCV valve.
- Test the new valve to make sure that it is operating properly.
There are several commercial PCV valve testers available. Be sure that the one used is suitable for the valve to be tested, as the testers are not universal.