Instructions
Use a screwdriver to remove the screws that fasten both halves of the gun together. Be sure to keep the screws in a safe place, and pull the two halves of the gun apart, exposing the inside of the weapon.
Find the trigger unit on the assembly. This can be found above the handle and just below the gearbox. Unscrew the top half of the trigger unit, making an effort not to disturb the mechanisms as you go.
Ensure that the spring is properly connected to the top half of the trigger unit and, if necessary, reset the trigger on its pegs. This spring mechanism is vital to the firing action of the trigger.
Use a small amount of machine oil to moisten a cotton swab and wipe the swab around the bottom of the metal firing plug. Wipe another swab around the trigger nipped at the bottom of the metal firing plug.
Re-assemble the gun by reversing your earlier step. If the gun does not fit back together or displays new problems, do not force the issue; call an expert.