Thank you that’s good advice. I think I might have been overdoing it a bit with the electric pump. I’ll also check the chokes. If I’m still having a problem I’ll check the floats, although I’ve never done that with a Solex!
I've owned my series 1 2c for 25 years , I realise the carburettors are different, but I've found once primed, with full choke my 2c starts first time.
However its a big mistake to touch anything until they have sorted themselves out, and rev to about 2000 rpm, then you can gradually push the choke lever in and use the throttle.
So, don't be tempted to touch anything, Hands and feet Off!