KJ Works 05 & 06 CO2 Mag Diagnosis & Fix

If It 'Aint Broke Don't Fix It
Unlike many things in this modern world the KJ Works CO2 Mags do have user-serviceable parts inside.
Don't be tempted to strip them for fun though, or just to have a look, the valve can only be removed and replaced a few times before the front seal, which is a consumable part, will need replacing.
if you do take the valve out the front O ring can often be persuaded to regain much of it's original form by swirling it around in a nice hot cup of tea - you can use freshly boiled water or steam direct from the kettle spout, it works just as well, I just usually have a cup of tea to hand.
If Your Mag is Leaking Gas From The Top
You'll need a Valve Key which are available from most Airsoft suppliers, and you really should have one if you use guns with anirsoft-type mechanism.
First tighten the valve slightly, If the leak reduces or changes the front seal is leaking slightly, depressurise the mag, replace the front seal if you haven't already or lube and reseat the front seal on the valve, refit & retest.
If tightening the valve doesn't change the leak depressurise the mag and remove the valve, be careful not to damage the brass firing pin if you have to pull the valve out with pliers once fully unscrewed, any burrs on the edge can cause the valve to jam in use.

Inspecting and Cleaning the Valve Seat

When you get the valve out hold the brass pin flush with the body and inspect the valve head and seat for contamination, a very small piece of dirt on the valve seat can cause the mag to discharge all it's gas in just a few seconds.

Even if you can't see any contamination it's still worth cleaning the valve and seat with a cloth or soft brush, if there is something stuck that a brush or cloth will not move use a cocktail stick or a rounded pencil tip  - never use anything hard or sharp on the valve seat, even a small scratch or nick will cause a major leak.

 If your valve front O ring wonn't regain it's shape in your cup of tea (or over steam from the kettle spout) you should fit a new seal, either way lightly lube with silicone grease, fit to the valve body and replace the valve and tighten gently.

Insert a new CO2, pierce and listen for leaks. If some gas is still escaping tighten the valve slightly. If the leak stops you're done!

If the leak reduces or changes but will not stop the front seal is leaking slightly, depressurise the mag, replace the front seal if you haven't already or lube and reseat the front seal on the valve, refit & retest.

If you still have a leak return your valve for testing and reseal service. 

If Your Mag is Leaking Gas From The Bottom
Remove the piercing cap and visually inspect the piercing seal which surrounds the pin, if the seal is missing fit a new replacement, to do this take a used 12g capsule and place a new seal on top, keeping the capsule vertical insert gently up into the mag and firmly push the seal into place.
If the seal is present but damaged remove it and fit a new one.
In the unlikely event that a new piercer seal does not resolve the issue the piercer block O ring should be replaced, details of how to remove the piercer block can be found below in the second method for removing a piercer seal.
 There are two ways to remove the piercer seal, either pull it out using a tool made from a length of wire with a bent point  
 or hold the mag in a soft jawed vice and use a large screwdriver to remove the piercing block 
 Then remove the seal, a Swiss Army Knife corkscrew is ideal for this, then just push a new seal in place with a used CO2 capsule,  lube the piercer block O ring with silicone grease and reassemble, be sure to replace the O ring if it is damaged.