[alantf]

re :- drain screw, cracked bowl, leaking gasket. Checked these again, & they seem o.k.
can't find the extra overflow - think it must be on another bike.

The vacuum hose on the back of the petcock also seems o.k. If this was the problem, wouldn't it also interfere with the efficient/smooth running of the bike while riding, & not just on start up?

As soon as I get a chance to "babysit" the bike, in the garage, I'll try letting it sit for a few hours in "prime"

Thanks, & if anyone can think of anything else please feel free. Once I try all the logical searches, it'll soon be time for "clutching at straws"