View single post by Jim Ketcham
 Posted: 06-02-2005 11:33 pm
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Jim Ketcham


Joined: 03-13-2005
Location: Salt Point, New York USA
Posts: 198
Hello Wayne,

The large breather hose that comes from the rear of the block goes into the "air box" on the factory original.  On later models the vent added to the top cam cover on the side of the oil filler inlet also goes to the "air box".  The air box in turn connects to the air cleaner housing.

It is undesirable to have the hose vent to atmosphere, especially in the engine compartment, both from an environmental and safety viewpoint. 

In my opinion, the air box venting also offers a bit of vacuum for the crankcase which, directionally, is a good thing to help limit seal leaks.  It is one of the reasons that I reinstalled the original type air box system on my JHs.  The main reason was that I found the Dellorto carb noise a bit too much with the K&N type filters.