I assume by two way you mean air can flow freely in or out of the valve? If so, a little technique can make prevent all the air from flowing out when
you pull the pump nozzle out. If you pinch the valve body then pull the nozzle out and are fast about putting the plug in, almost no air should leak
out.
What I am concerned about is that you are flying an old C-kite. Those are dangerous kites without much depower and lack safety features of newer
kites. Many people have been seriously injured by these old kites. If this kite is anything more than a light wind novelty, I would recommend finding
a newer kite as it will be much easier and safer to fly.
Arcs - Charger I 8m, 10m, 12m, Venom I 13m - F-Arc 1200, 1600
Single Skin - Born-Kite LongStar2
Fixed Bridles - Pansh Legend 4.5m - Peter Lynn Voltage 3m