I've left the fuel tap on for over a week now and the needle and seat isn't leaking any fuel and 2 primes and the mower starts.
I was looking at one primer cap with a magnifying glass and where the taper is cut in the seat there was a bur sticking outward, this makes me wonder when people have problems with the needles if you just need a milling tool to remove a bur.
If there was a problem with the seat in the cap you could make an alignment tool in a lathe to centre the seat in the cap and make a tool to polish the seat in perfect alignment using valve grinding paste.
