Vacuum Leak

[Strop]

Was doing some tune up work on the 82 Westy yesterday and noticed that when I pinched the vacuum hose that runs between the s boot and the black breather unit that plugs into the hole on the top of the block - my engine vacuum kicked up 2 inches and the idle smoothed out noticeably.

Need to know if anyone has experienced this phenomenon, is this a normal occurance, etc...

To me gaining a solid 2 inches of vacuum at idle tells me something aint right. That extra 2 inches should be there all the time I would think.

Any input appreciated as I need to know whether or not I need to pursue this or leave it be as it is normal behavior.

Thanks........

[Amskeptic]

Was doing some tune up work on the 82 Westy yesterday and noticed that when I pinched the vacuum hose that runs between the s boot and the black breather unit that plugs into the hole on the top of the block - my engine vacuum kicked up 2 inches and the idle smoothed out noticeably.

Need to know if anyone has experienced this phenomenon, is this a normal occurance, etc...

To me gaining a solid 2 inches of vacuum at idle tells me something aint right. That extra 2 inches should be there all the time I would think.

Any input appreciated as I need to know whether or not I need to pursue this or leave it be as it is normal behavior.

Thanks........

The crankcase is plumbed into the air intake side. A fresh engine does not have much in the way of blowby making it into the crankcase past the rings and valve guides, a used high mileage engine will. This is metered air, air that was already measured at the AFM on its original path into the engine. But! A leaky dipstick hat/dipstick boot/front seal/cracked oil filler/valve cover gasket/breather gasket can all allow unmetered air in. The drop in vacuum you are experiencing is normal. Check the decel valve for full closing too.
Colin

[Strop]

Thanks ...