AK47 Disassembly and Upgrade Guide

Well as a stock rifle, the AK is fairly boring. It's only fair to fit a Systema Power FTK (Full Tune-up Kit UK Level 1), so it was decided to buy and fit one. Again, as with much of our equipment, it was bought from WolfArmouries . The Systems FTK includes:

  • new cylinder and cylinder head
  • new piston
  • M100 Spring
  • new spring guide rod
  • new gearbox end (the snap-on sheet that holds the two tops of the gearbox sides together)
  • 6x new metal bushings
  • new nozzle
  • 3 new helical gears
  • 2 washers (for the drive gear)
  • new non-return lever and return spring
  • valve movement lever (black plastic about 3 inches long)

You'll need these tools: philips/flat head screwdrivers, allen keys, torx bit set, long-nose pliers, silicon grease, tac hammer and a small torch

IMPORTANT: Please note, this article is correct to the best of my knowledge. Taking a gearbox to pieces, and upgrading it, is the most complex thing that you can do to an airsoft weapon. If you are not confident that you know what you are doing, I'd recommend that you consult someone who is, and get them to either aid you, or watch over you as you do it for the first time. This website, and it's members will not be held responsible or liable for damage to anyone or anything resulting from information or advice contained herein.

Please note that this is only the first draft of this guide, as such, it will be upgraded and updated regularly when I have the chance. The information has yet to be verified and proof-read, so they may be errors in the following text.

Part 1 - Stripping the rifle

The first thing to do is to remove the stock, and the magazine. To remove the stock, remove the but-plate, take the battery out of the stock, then, simply undo the 2 screws on the underside of the stock. Remove the stock, and set the hop-up on the rifle to zero, or the minimum setting.

When you get the stock off a few centimetres, you'll notice that there is an electrical cable passing through the join. Simply unplug this cable at the connection that you find as you pull the stock away from the receiver.

You should then remove the top cover (covers the battery). This can be removed by simply depressing the sprung button at the rear and lifting the cover up.

Next you should remove the pistol grip cover.

Unlike other AEG's such as the G3 or MP5 the screw on the bottom holds the cover on, rather than setting the gearbox pressure on the motor.

As you take the screw out you can just slide the grip off pulling it away from the rifle body.

The next task is to remove the top receiver cover, that holds the cocking handle, and the dummy battery cylinder. If you have an AK with a folding stock (the AK47s), this will hold your battery, rather than a dummy cylinder.

The top cover is held on by 2 screws, this is at the front left of the cover, it's tiny, with a philips head.

The other screw that should be removed is the hop-up adjustment handle, this is the piece of plastic that you move back and forth to adjust the hop-up. This is hidden behind the cocking handle. You'll need to hold the cocking handle back, and then remove the screw that holds this tiny piece of plastic on.

The final part to undo, to get the top cover off, bar that provides the spring action for the receiver cover button. This is a piece of steel (a long bar about 5mm in diameter) that runs the length of the top of the receiver.

This is located in the back of the metal button you push to release the top cover. To get the spring out, simply use a flat-blade screwdriver and pry the spring out.

The button won't go anywhere when you detach the spring, as it is attached to the gearbox in a enclosed slide. The button will come out later when you separate the sides of the gearbox.

The top half of the receiver simply slides back (towards where the stock goes), then it comes off upwards. This should leave you with the top of the gearbox exposed.

Please note at this point the position of the red wires. It is important that when the gearbox is placed back that all the wires go back to where they came from, and are not pinched by the sides. Position of the sling point that you can see on the side of the rifle, should also be noted. The clip is held in with an 'L' shaped piece of steel that will fall out the second you turn the rifle upside down. So watch out for it.

The piece of steel sits inside the plastic of the lower receiver shell, and stops the sling clip pulling out of the side of the rifle.

In order to extract the gearbox from the receiver there are a few things that need to be done. Firstly the fire-select handle needs to be removed.

This can be done at any time before the gearbox is removed. I actually removed it before the top of the receiver, as you can see in the photo.

The handle is held on by one philips screw. To get to the screw, simply pry off the steel cap that covers it with a sharp-ish flat-blade screwdriver. When the cover is off, simply undo the single screw and take the handle off.

The next thing to do is to separate the 2 halves of the rifle, the receiver and the barrel assembly You should be able to see the join, which is just behind the top backsight. Unlike the G3 the gearbox needs the rifle to be separated from the hop-up unit before you can take it out of the receiver case.

To separate the 2 halves is a fairly simple process, but should be done carefully as the hop-up mechanism is fragile, and any damage to the rubber 'O' ring inside it would be fairly expensive (for what it is), and fiddly to fix.

It's important to support the rifle as you take the four screws out. You do not want the weight of the rifle to bend the join between the two parts.

To take the 2 halves apart, locate the 4 screws on the underside of the rifle, between the trigger guard and the foregrip.

Two of them are recessed into the area when the magazine locates itself, near the bb entrance to the hop-up. The other 2 are located near the foregrip. You'll need a number 2 philips screwdriver to remove these 4 screws.

When all 4 screws have been removed, you can carefully pull the 2 parts away from each other. This will leave you with the 2 parts as is in the picture to the left, with the gearbox on the left and the hop-up on the right.

You can put the barrel assembly to one side, as it's not needed until you begin to reassemble the rifle after you have finished working on the gearbox.

Now, to remove the gearbox from the receiver housing, you will need to remove the four screws located on either side of the steel bracket that the butt was attached to.

When these screws have been removed you should be able to carefully slide the gearbox out of the casing. It might be a little tight, as the trigger will touch the case as you pull the gearbox out. Simply depress the trigger in a firing motion and the gearbox should come out easily.


Part 2- Disassembling the Gearbox

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.

Part 3- Fitting the Systema Parts

The first thing to do is to remove the piston/spring/cylinder set. This is the brass cylinder, and the white piston inside it, with a spring attached.

There will be plenty of grease around, all over the gears and on the cylinder, so I'd recommend keeping a roll of kitchen roll handy, to wipe it off your hands, as it makes it very difficult to handle things.

The brass cylinder will have a black plastic nozzle attached to the end, and a long plastic lever along the bottom of it. Keep the black plastic nozzle handy, you'll need to put it back later.

You can now remove all 3 gears from the gearbox, and place them to one side. You won't need them, as they will be replaced.

On the underside of the lower of the 3 gears you'll find a small spring loaded leaver, note it's position (including the spring) then remove it, as this too is replaced by a better Systema part.

The next thing to replace are the bushings (there are 6 of them). These are basically bearings, that the ends of the gears revolve in. The replacements are metal, whereas the originals are nylon, and simply not up to the job of higher speed and power -they melt if used with advanced gearing. Simply 'punch' out the old ones and snap in the new ones.

Now is a good time to construct the piston. For some reason Systema ship this kit with the piston in parts (unlike a G3/MP5 kit). The piston consists of a piston head (red faced), a piston, a screw mounted in a black plastic end, 2 washers and a 'ball-bearing race'.

You'll need a bit of patience to do this and a long No2 philips screwdriver. Now take the black plastic piece with the screw in it, thread a washer, the ball-race then a washer over the end of it. The idea is to screw the 3 washers, onto the inside of the piston, through the small whole at the end and into the piston head, which is outside.

It's a real bummer to do, as you need to balance the lot on the end of a screwdriver inside the piston, and then screw it onto the pistonhead outside.

Make sure you screw this in fairly tight, you don't want the piston head coming off while in use, as that will make a mess.

Good luck.. it took me 5 attempts to get it right.

When that is done, u can place the new spring, inside the piston (it'll butt up against the washer assembly you have just screwed inside). Then you place the guide rod end into the other spring end (i.e. the one not in the piston).

Now the next bit is fairly complex so I'm going to rely on a few pictures, much more than normal, to show you what I mean.

There are 3 gears to put in and a small non-return lever with a spring on it.

Assemble the cylinder set, this is made from the ribbed cylinder, and the solid brass end. The brass end needs coating in silicon grease where it will touch the cylinder, and around the rubber grommet. Then place the brass end inside the end of the cylinder that does not have a flared end.

Now for an important bit of information: In the Systema FTK there would have been a bag with 2 teenie tiny washers in it. Carefully open this bag, the two washers are of different sizes, one is larger (and thicker) than the other.

(The following directions are in relation to the gearbox images shown below) The small washer goes on the top of the main drive gear (this is the one that drives the piston) . The large washer goes on the UNDERSIDE of the main drive gear between the gear, and the new metal bushing you recently put in. This washer needs to go under a small lever you'll find there, simply slacken the black screw that holds the lever down, slide the washer under that lever, then tighten the screw back up; but make sure that the lever can still pivot easily, so don't over tighten it.

Before the next set (the adding of the gears) you need to grease EVERY moving part with silicon grease.

The bushings need plenty of grease too, as do all the contact points where the gears either touch, or get close to each other. Don't worry about the mess the more grease the better (within reason).

Coat the inside of the new cylinder with grease, and the piston head, the nozzle and the piston itself - specifically the gearing on the piston side where the drive gear will mesh with it.

The first gear to put in is the one that goes in the middle (large flat and thin), place it with the large flat side to the bottom. The next thing to add is the spring loaded non-return lever, exactly as the original was., While holding this back, place the next gear in (the one without holes in its side).

The last gear to add is the main drive gear, this should be inserted as shown in the picture, in this EXACT position. In this position its just ready to draw the nozzle back, via the large black lever, and pull the piston back.

When you are certain the gears are in, turn them (they'll only turn one way) a few revolutions to make sure that the gears are free. When you are sure that they are free moving (there should be very little resistance) set them back so that they are in the same position as the image to the left.

Now you have all the gears in the correct position, you need to put the replacement cylinder and piston set in, after you have attached the new nozzle movement lever, and the return spring that goes with it. You can see the return spring circled on the image to the right in red. This spring is attached to the gearbox by a protruding pin, and to a leg on the nozzle arm.

The black nozzle arm, attaches to the black nozzle (small back cylinder) and goes over the end of the new cylinder end (the brass cylinder with a hole in each side). In this position, when you move the arm back and forth the black plastic piece should move back and forth in turn over the brass pipe.

You should find that the head of the cylinder fits nicely into the gearbox, and that a protrusion from the gearbox face, fits into a hole on either side of the brass nozzle end.

With the cylinder in, you can place the spring, with guide end, into the end of the piston - obviously the guide rod, goes at the opposite end to the piston.

Now comes the difficult part, you need to compress the spring, and locate the guide rod end in the hole at the back left of the gearbox (you should see a thin rectangular hole where you poke the metal protrusion from the guide rod.

It takes a bit of practice, but it's easiest if you keep the cylinder held down onto the gearbox with a spare thumb, otherwise it may fly out if the spring breaks loose and/or slips.

It's normally easier to handle the spring, after you have cleaned your hands of silicon grease. =)

When the spring is in the right place, you can attempt to place the other side of the gearbox on, while holding the spring down. It'll take a bit of tweaking, as the gear axles need to be located in the correct holes, as does the cylinder etc., so you may need to poke a sharp thin screwdriver in to poke things into the correct place.

When the 2 sides are together, fit the screws, and secure the 2 sides together, then attach the replacement top cover for the gearbox, and slide it on, from the cylinder end first. I found I had to tap mine (LIGHTLY) with a small tac-hammer to get it to slide on. You may wish to grease it a bit to ease it on.

Part 4- Rebuilding the Rifle

Now you simply need to follow parts 1 and 2 in reverse to put the gearbox back in. There are some points to note though, throughout assembly.

When you rebuild the fire-select lever system, make sure that the gear on the back of the gearbox is secured at the correct point, in the plastic gear rack - you'll notice that the plastic rack, and the gear have a large gear lug cut into them, these should be aligned.

To align the gears and levers on the other side, you can find on the left and below three images that show what you should have. Basically, with the black plastic rack at it's maximum extent (pulled out all the way) the opposing lever on the other side should also, in turn, be at its maximum extent.

In this position, the fire-slect elver is in 'Full-Auto' mode

In this position, the fire-select lever is in 'Safe' mode

When you put the gearbox back into the receiver housing, you should make sure that you do not pinch the red wires. There is a gully cut into the plastic for them on one side of the gearbox - see image to the right.

You'll find that if you have the cables in the wrong place, the top cover (that covers the battery) will not go on properly.

When everything is back together you should have a pile of spare parts,

I'd recommend putting them back in the Systema box for safekeeping, you may need them in the future.

When you go to fire the rifle for the first time, I'd recommend firing a few shots, to ensure everything is ok, rather than blasting away on full auto. If you have (for some reason) got a problem in the motor/gearbox, the fuse in the stock will blow - this is an indication of something being jammed that causes the motor to either be put under excessive strain, or to not turn at all. If this happens, strip the rifle back down to the gearbox, crack it open, and have a look, as you've got something fundamental wrong inside, like a gear out of place.


This page last updated Monday, May 28, 2001 2:34 AM

All images and content are copyright 2001 ArniesAirsoft