This is possibly one of the more difficult tasks to do, on the disassembly side of things. One of the problems of taking a gearbox to bits is that there is a highly compressed spring running across the top inside the chassis. With an AK gearbox, this spring is held in place at one end by the cylinder (the brass tube), and at the other by a rectangular piece of metal, that is secured into two holes on either side of the gearbox chassis. This spring will fly out, given half a chance. As a precautionary measure, make sure that there is nothing breakable behind the motor end of the gearbox (the end that doesn't fire) like your eye or your friends head - this is the end that the spring will fly out of if you are not careful.

Before you can get into the gearbox you'll need to remove the gear assembly that controls the fire-selector lever, from the outside of the gearbox, and detach the motor. To detach the motor, simply remove the 2 screw at the corners of the metal frame that holds the motor. When you have removed these screws, simply carefully pull the motor away from the gearbox, and set the motor to one side. The motor will still be attached to the gearbox by the electrical cables that are attached to the firing circuit, so make sure that you don't pull the wires around too much, as you might sheer the points where the cable is soldered to the motor.

Before removal After removal

Now you must take off the 'fire-select' assembly. This is made of 4 pieces of metal. There are 2 parts on one side, an 'L' shaped piece of metal, and an 'A' shaped piece it connects to and sits on. The 'L' shaped piece can be removed by undoing the screw that you can find in the centre of it. The 'A' shaped piece is merely held in place by a pivot, so it should come off very easily. Don't worry too much about the position of the parts, they are all handed, and it's fairly simple to make sure that you get them together correctly when you come to reassembling the lot afterwards.

Of the rest of the assembly, 2 parts comprise a pivot that runs through the gearbox from one side to the other (held together by a single black screw). Remove the black screw, and you should find that the pivot comes into two pieces, with one part on either side. Please note the placement of the metal gear on the side, into the black plastic rack.

To gain entry to the gearbox, you'll need to separate the two halves of the chassis. First you should remove the large piece of steel clipped over the top of the gearbox. You simply slide it towards the valve end of the gearbox, using a flat blade screwdriver. Don't worry too much if you bend it as there is a reinforced replacement part in the Systema kit - obviously it's better to keep it in good nick though.

After you have safely removed the top cover, carefully remove all the screws on the outer edge of the gearbox. You should find that some screws are torx heads, and some are philips head. When you remove the last screw, the 2 sides of the gearbox should stay together, as they are a very tight fit, they may not so, so be careful that you keep the gearbox on a level flat surface, so that nothing can roll out. To ensure that the gearbox doesn't 'explode', keep a firm and constant pressure on the brass cylinder, it's normally easier to get a friend to do this for you while you undo the screws.

When all the screws have been removed, you'll need to remove the black plastic cover that's behind the trigger, this covers the edge of a gear that sticks out the side of the gearbox. Now for the real tricky bit. You need to carefully pry the 2 halves of the gearbox apart, while not allowing the spring to get too loose. I use a fairly sharp screwdriver, lifting the 2 sides apart from the bottom, near where the motor connects. When the 2 shells are almost free of each other I put my finger inside (if there's room) or another screwdriver to hold the end of the spring in place. If all goes well you should end up with something that looks like the photo to the left.

NEXT - PART 3 - Fitting the Systema Parts