Had the same problem when I had a single Roch "B" on my 261. Always had to prime it with gas or use "Nitro" in the rattle can. When I changed to my dual Holley Webers I thought the problem would go away but even with an electric choke, if it sits for a couple of weeks, I need to pump the pedal several times to get it started. Not a real problem but it still give me the impression that the fuel is evaporating in the bowls after sitting a long time.

Country Roads, West (By God) Virginia
http://community.webshots.com/user/geezer