I wanted to use my 7m yesterday, but it had a leak. I hate showing up for a session only to have kite gear fail and keep me off the water. It was time for some maintenance. I pumped up the kite today and used the soapy water in a spray bottle method to find the leak. The stopper for the main valve was leaking slowly due to a loose fit. The following is how I fix this problem.
What you needCheap pen like the typical Bic pens you had in school. The back end of a properly sized Drill bit works well too.
Small zip ties
Small pliers
Small “diagonal cutters”
Coffee cup with water as hot as you can work with comfortably.
Step 1: Remove the stopper from the tab connected to the valve and the Velcro attached to the kite. Use the pliers to hold the stopper in the cup of water until the plastic is warmed from the water. 20 seconds or so should be good enough. Quickly shove the blunt end of the pen into the hole in the stopper and let it cool to room temp. You can speed up the cooling by dipping it in a second cup of cold water. Taking this step will slightly expand the stopper
Step 2: Put a zip tie firmly around the valve just under the collar at the end of the valve. An option would be to add a second wire tie just below the first one. Dip the valve in the cup of water long enough to heat up the valve. Make sure you do not put the valve flange where it is glued to the bladder into the hot water. Heating up the flange may cause the glue to fail. After the valve is heated to the water temp, remove it from the water and quickly tighten the zip tie once again using the pliers because it is wet. Let the valve cool. If you leave the wire tie on the valve it will probably be too tight to put the stopper in. Snip off the wire tie with the diagonal cutter and reattach the stopper to the Velcro and valve tab.
Valve with zip tie tightened a second time and left to cool.
The valve and stopper should now have a tight fit and work fine. An option would be to re-add a zip tie (same position below the valve collar) and tighten it down to the valve while the stopper is in . If you do this, try sliding the zip tie head so it is under the stopper tab after you snip off the excess zip tie plastic tail. This will help protect your hands and kite from the sharp zip tie head.
Disclosure: I am sponsored by the Krispy Kreme kite boarding team. PM me for demos.