probably better off replacing valve with stick on. They are cheap and it's probably a bit more reliable than trying to reglue.

New valves are easier to put on and much easier to stick on and more reliable

http://www.kitepower.com.au/fixmykite-9mm-inflate-valve.html

you can order online, over the phone or come into a shop and have it fitted

Vinyl pool cement (urethane) or neoprene glue from a dive shop works best.

Use a 5kg barbell weight over the valve to hold it in place while its drying--and make sure the glue doesn't go into the hole or you're stuffed!

1. Buy a stick on. The North ones are excellent.
2. Pull the valve out of its hole without removing bladder from kite... Pull about 6-12 inches of bladder out with it. Yes... It will come out...
3. Remove old valve
4. Spread bladder FLAT over the side of a pump. Ie pump between kite leading edge and bladder.
5. Get ya mate to hold the bladder tight over the side of the pump while you stick the new valve on nice and flat like...
6. Stuff it all back in the hole (only hard bit of the whole process) bit by bit... Again... It will go, you jus gotta ask nicely....
7. Align bladder and pump up gently... Check!
Should take about 5 mins total

Agreed my bro and i changed three in about 20 minutes yesterday morning, out kiting that arvo.

Try " STORMSURE " from Clark Rubber and others.

Needs 12Hrs to fully set and its a good idea to hold the valve down with a weight.
I use a dive weight on top of a roll of tape.

Have used the stick on patch variety also, recently had one of the $35 quick fixes fail on the dump valve. the valve detached itself from the sticky backing.

Perhaps I should buy some new kites as this seems to become a problem with kite age.