PCV BREATHER CRANKCASE VACUUM NON RETURN VALVE

FITTING BREATHER VALVES HAS BECOME POPULAR AS THEY ARE QUITE GOOD AT PREVENTING OIL LEAKS AND CAN HELP WITH THE 850 COMMANDO POROUS HEAD PROBLEM, (LEAKING FROM THE FRONT OF THE CYLINDER HEAD AROUND 3 FINS UP).  ANOTHER REASON FOR FITTING THEM IS A SMALL INCREASE IN PERFORMANCE IS OBTAINED (SUPPOSEDLY).  ANOTHER SCHOOL OF THOUGHT CONSIDERS THEM TO INTERFERE WITH OIL DISTRIBUTION IF THE ENGINE IS RUN CONSTANTLY AT HIGH SPEED ALTHOUGH THAT SEEMS TO APPLY ONLY TO SOME HIGHLY EFFICIENT READ VALVE TYPES.  IN 1973 NORTON'S THEMSELVES DESIGNED ONE VERY SIMILAR TO THIS ONE ALTHOUGH IN THE END THEY OPTED TO MOVE THE BREATHER TO THE BACK OF THE CRANKCASE.  THE VALVE WOULD BE FITTED IN THE ENGINE BREATHER PIPE, LARGE DIAMETER (APPROX. 1/2") IS IN AND THE SMALLER 3/8" DIAMETER IS OUT WHICH WOULD NORMALLY FEED TO THE OIL TANK, A CATCH BOTTLE OR ON SOME BIKES THE END OF THE REAR MUDGUARD.

THIS VALVE WILL ALLOW SOME REVERSE FLOW.