Hi
I'm fettling the bike ready for a ride to the Somme Battlefields in a while and need some guidance to fix some niggles

1)
Bike appears to be running slightly rich on one side and I think I need to change the float needle valve and seat. Delorto UK offer a range of sizes. Can somebody confirm a 300 (whatever the units are) is the size on the PHF36s?
2)
The oil seal on the output side of the gear box was leaking in to the bevel box so I changed it. Bad news is it still is

I'm sure I didn't screw up the fitting of the new seal so could somebody please advise why its still passes oil.
1st thoughts are breather not breathing

Cheers
Tris