[AT] cub / prime oil pump

[H. L. Staples]

Walt  a gear pump will not pump air as well as it will oil because of the
necessary clearances within the pump and the fact that air is so much
thinner than is oil. 

I have always been told to pack a new pump with light weight gun grease so
that all the air spaces are filled. If a gear pump were made with zero
clearance so that there was no air space then the pump would also be locked
up.  

Vane pumps do a pretty good job of pumping air until the vane ends become
worn and allow slippage or bypass.  

 
H. L. Staples
McLoud, Oklahoma
USA