Take the grip frame off of the leaky one and push the cart valve out. Don't take it apart yet but take a pic of the front end of the valve. The most likely culprit is the face seal and should be pretty obvious if it's damaged.
Note: While I would love to take credit for his work, I am not associated with Mad Customs!
Originally Posted by senghing27
You can contact BigMatt-MadCustoms in his MCB forum