Gentlemen :

I removed the vent hose through the inspection port and blew it out with my mouth, I think it was clear of any obstructions as air came out of the filler hose .
Then I removed the petcock from the fuel pick-up line into the tank , cut the fuel line and blew compressed air into the fuel line and tank to clear any obstructions . I eliminated the petcock and connected the fuel line directly to the pick-up .
Tried primming the ball , still no fuel . Removed ball from line and checked it out , appeared to be working fine . Pulled fuel from the tank using auxillary pump thru line and water seperator then reconnected ball and primed carb's. Engine started up OK .
I am thinking my problem was that the ball was in a vertical position and can not work adequately in that position. When I replaced the fuel line two years ago I left it to long , causing it to hang vertically .
Hopefully this has cured the problem , I thank you all for your responses.

The Engineer