G'day Norm,
All these problems with the needle and seats ,I'd be sanding a little off the
side of the float to make sure it's not the float sticking on the side of the
carby housing, you can test the seat and needle before fitting the
primer cap by holding the needle down and blowing on a hose connected
to the primer cap fuel line spigot, you've probably done that a million
times before.
That's what I also do to check the needle and seat are sealing and
the needle isn't sticking but if it's slightly leaking you may not notice
without using a pressure gauge.
Cheers
Max.
