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Intake Manifold Question

McFly

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1979 CB750F I am trying to get the carbs removed to clean them. There is a tube at the back of the intake manifold that goes to a small box underneath battery. From there it goes to drain hose under bike. What is this little box for? This tube is on the vacuum end of the manifold beyond air filter... I am confused what the small box is for.
 
Not vacuum, rather crankcase pressure. Call it PCV hose as that is what it does. The half inch hoses at back of both sides of engine go to a tee higher up that goes through airbox and vents inside then continues to the box under battery. Vapors pull off inside the airbox to burn and then oil solids drip into box to be emptied from time to time.

It's pollution crap.
 
Nope. It is not the PCV tubes that go to a plastic T and then to the air manifold. It is another tube that goes to a smaller 1/4" tube or 3/8" tube and then to a little box underneath battery bracket. It collected a bunch of oily fluid.
 
Wrong, the PCV hose comes back off the back of the airbox (not manifold) again to join that box under battery. It's a split hose system. Hose goes to airbox to pull vapors off by carbs then continues to battery with solids left over if any to dump in that box. You check and empty it from time to time. Why your 'oily fluid'.
 
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