Disassembling the AML K4

OK, so since the Accucraft people connected the track pickups, a power regulator board and the motor all together inside the boiler, any power conversion requires taking it apart. (As I've stated before, this was completely unnecessary since there are plenty of extra contacts in the connector between the loco and tender to allow these wires to come individually over to the tender).

Note: when placing the locomotive upside down in a cradle, be sure to not damage parts on top. I loosened the whistle and rotated it down towards the boiler. Watch the bell also.

To take the boiler off, you need two sizes of wrenches, the one supplied with the locomotive, a 3mm, and a smaller one, which 2mm, which fits most of the small hex head bolts you see on the loco.

There is also a 1.5mm hex wrench supplied, this is for the set screws on the universal coupling on the driveshaft.

There is also a very tiny allen screw on the reverse mechanism, it's  0.9mm.

Sources for tools:

I found an 00-90 wrench which was a bit tighter on the small hex bolts, but very close to 2mm.

I found a hobby store that had a selection of small screws, and they had 00-90 hex bolts and an 00-90 wrench. This was a bit of a tight fit on the AML bolts, but I bought some 00-90 hex bolts, and used a bit of valve lapping compound to open up the nut driver/wrench. I measured the AML bolt heads, and got .086" which translates to 2.18 mm... The wrench I found was from "hob-bits", which seems to be from Woodland Scenics the wrench is part number H885.

Remove the cab:

The first thing I did was remove the cab. Apparently this is not completely necessary, but not too hard to do, and makes it somewhat easier to remove the boiler.
Turn the locomotive over, and remove the 4 small screws on the corners of the cab from underneath. One is particularly hard to get to.

Pop the handrails off the bottom of the back of the cab, and then pull back a bit. One of the steam lines that goes across the boiler has a right angle bend in it so you need to look inside the cab to see how to turn it to get it off.

Remove the ash pans:

While still upside down, remove the ash pans. They are ahead of the cab on both sides of the firebox bottom. Since they wrap under the firebox, the boiler can't be pulled up as the ashpans will hit the lead weights that are mounted on the frame inside the boiler.

They are short strips of metal, each held on with 2 small 2.0 mm hex head bolts.


 Remove cab to frame angle brackets:

There are 2 angle brackets that secure the cab floor to the frame. Remove the 2 screws on each bracket that screw to the frame while the loco is on it's back.

Now turn the loco right side up.

Remove the other screws holding the brackets, for each bracket, there is one slotted screw and one Philips flat head screw. It helps to support the underside of the cab floor when removing them. Tip: mark the brackets with L and R in a black felt marker, it can be confusing when putting them back on.

Remove linkage for reverse gear:

Also on the reverse gear there's a 3mm hex bolt that needs to be removed to disconnect the linkage. It's located on the engineers side running board above the first driver...the linkage comes through the running board. There is a small spacer there too. (The simulated steam piston stays on the boiler, and the linkage stays with the chassis.)

Now you have an alternative. Rather than removing the entire boiler as a unit, you can leave the smokebox attached to the loco and skip removing the front steps, diagonal braces and smokebox front. Remove the small hex bolt on top of the boiler just behind the stack. If you do this, skip ahead to "Remove Cab Floor". (This tip courtesy of Jim Carter.)

Remove the front running boards and angle braces:

I was advised to remove the front short running boards and brackets that are bolted onto the smokebox, note the longer screw goes into the bottom hole, this helps in reassembly. Then remove the diagonal braces that run from the smokebox down to the front pilot beam. Remove the screw on the pilot end, the smokebox end just sticks inside.

Remove the headlight and smokebox front:

Remove the four 2mm hex bolts that secure the headlight to the boiler. Gently pull the led out from the back and remove the headlight. Now remove the 3mm hex hex bolt that was right under the headlight. The smokebox front just lifts off.

You can now see a big 8mm hex nut holding the front of the boiler to the steam cylinder saddle. Remove it completely. Don't worry about the screw dropping out of sight, you can reach it from underneath to push it back up when you reassemble. In fact, you should push it all the way down to help remove the boiler.

 Remove cab floor:

I took the cab floor off, 4 slot head screws along the back. Work the cab floor backwards and up to clear (it has some stuff hanging underneath, just look and lift it up just enough to clear).

 Remove the rear bulkhead screws:

Now look into the back of the engine, the socket sits in a trapezoidal opening. Look above the ends of the socket, and further in. You can see 2 slot head screws that go into the boiler.


They are about 1 cm long, use a pair of needle nose pliers to take out.

The boiler will now come off, and you will need to unplug the wires for the marker lights and headlight. The wire for the smoke unit is just loose up insdide the boiler.

Here's the loco with the boiler off:


Well, that's it, put it back in reverse order!



I added a washer under the 8mm nut in the boiler, so the nut is not pressing directly on the boiler shell.

You might want to use some touch up paint on the hex bolt heads after putting back together.

While inside, it's a good idea to check the tightness of the two 1.5mm allen setscrews on the universal coupling. (Don't ask me how I know!)


There are 10 small screws underneath that hold the tender shell on. Be sure not to tear the marker and rear headlight wires out.



Weather Underground PWS KCACARLS78