Coleman and AGM 520/M1941 stoves

This model stove was used by the U.S. military during World War II. The Coleman version is called the 520 and the American Gas and Machine (AGM) seems to go by model M1941, but it seems that the 520 is the manufacturer’s designation and M1941 is the military designation. I think using either is fine, but it seems like most people call the Coleman a 520 and the AGM, M1941. I have three of these type of stoves an AGM model made in 1941, a Coleman made in 1943 and a Coleman made in 1944. If you’re interested in stoves like this be sure to check out the forums at Coleman Collectors Forum and Spiritburner.  There’s also a brief history of this stove on the wiki. After a period of observation and study, I became aware of the somewhat minor differences between them. I decided to enter it on my blog so I could use it as a reference. I’ll probably add to this post from time-to-time.

(left to right) 1941 AGM, 1943 Coleman, 1944 Coleman

(left to right) 1941 AGM, 1943 Coleman, 1944 Coleman

Tanks

AGM Tanks

AGM tanks are made from steel for 1941-1943 and then brass for 1944 and 1945 (Update 15MAY2016: In the last few months I’ve seen two 1944 AGM tanks which were steel. So, either the information I had is incorrect or AGM switched to brass during 1944 resulting in some 1944 tanks being made from steel and others made from brass). AGM made the brass tanks too thin and they have a tendency to crack or split, and I now have one of these. One of the previous owners wrapped the tank in thin sheet metal and soldered the whole thing. It’s really ugly, but might actually work. I consider it a loss. If you ever plan to buy a brass-tank AGM, be sure to look closely at the tank and check that it holds pressure. Steel tanks are generally more solid, but they rust and some will develop pin holes, so they need to be checked as well. As far as I can tell all AGM stoves of this model had three fold-out feet. The tanks have stamped in the side, U.S., year, AMERICAN. The fuel fill opening is the standard diameter of newer Coleman white gas appliances.

Added 27NOV2016 – Since this messed-up 1945 AGM stove was not something I thought I would probably sell as a stove, I disassembled it, removed the steel wrapper and cut it open. The two photos below show how the AGM tanks split and what the inside of a 520 stove looks like.

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The split sides of the AGM 1945 brass tank

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Cut-away inside view of a typical 520 tank

Coleman Tanks

Coleman tanks vary a little bit more. The 1941 tank is nickel plated brass, I believe. These are really pretty rare as only 1,000 were made. The 1942 and 1943 tanks are steel, while the 1944 and 1945 tanks are brass. Coleman brass tanks were made better, or thicker (?) and seem to be less prone to cracking or splitting. As with AGM tanks it’s best to inspect carefully. Unlike the AGM, the Coleman 1941 and 1942 years had four fold-out feet instead of three while 1943-1945 had three. The tanks are labeled U.S., year and Coleman. The fuel fill opening is the smaller type for 1941-1943. The 1944 and 1945 use the larger size.

Check Valve/Pump (Edited 27NOV2016)

AGM and Coleman used different check valve designs and pumps and they are not generally interchangeable. Coleman used the one piece ball check valve with a stem. The square stem post was operated by the pump handle and is similar to more modern Coleman stoves like the popular 502 or 400 series stoves and like most lanterns. The AGM design used a two-piece ball check valve without a stem (Update 15MAY2016: Recently, I received a 1945 AGM which has the Coleman-style check valve and pump handle. I don’t know when AGM changed their design, but the 1945 tank I have used the Coleman-style design). The pump operated the rotating part of the check valve. BTW – That little steel ball in the check valve can get stuck preventing the tank from pressurizing. Sometimes, it can be cleaned without removing it, using some solvent, like carburetor cleaner. I’ve done this successfully.

520 pumps and check valves, AGM (top), Coleman (bottom)

520 pumps and check valves, AGM (top) minus the lower part which is similar to the Coleman shape, Coleman (bottom)

520 check valve, bottom view

520 check valve, bottom view

Valve Assemblies

The valve assemblies seem to be pretty much the same. The valve stem, valve body, eccentric block looked nearly identical on the stoves I’ve disassembled. Minor differences include the F/A tube (fuel/air tube which picks up the fuel from the tank), tip cleaning assembly, and the packing bushings.

Here's a 520 valve disassembled

Here’s a 520 valve disassembled

Here the 520 valve is assembled with vaporizer nut/spirit cup added

Here the 520 valve is assembled with vaporizer nut/spirit cup added

One thing I learned from lanternking is that the M2 pre-heater/burner assembly uses the same valve stem as the 520, except for one difference. The original valve stem uses a 4-36 size screw to attach the knob, while the M2 valve requires a 4-40 screw. The valve stem was broken on my AGM and needed replacing.

Above is the M2 burner valve stem, below is the broken 520 valve stem

Above is the M2 burner valve stem, below is the broken 520 valve stem

Vaporizers

The vaporizers are the same for both manufacturers and all five years of the stoves. Note that the vaporizer tip can be removed. This was helpful to know because the screens were so clogged with carbon that the vaporizer wasn’t very useful. If you remove the tip, you can use something to push the old screen out so it can be replaced. If the tip itself is plugged you can sometimes use the old tip cleaner needle to open it up again.

520 vaporizer parts

520 vaporizer parts

Some stoves also had a spirit cup (what we would probably call a preheat cup today) and I don’t know if these were common or not (see valve assembly photo). My 1941 and 1945 AGMs and 1944 Coleman had these, while my 1943 Coleman did not. These are used by adding alcohol or fuel to the cup and lighting it. After letting it burn until it almost goes out, you turn on the main valve to light the stove.

On/Off Valve knob

One quick way to identify a Coleman versus an AGM stove is by looking at the main On/Off valve knob. The AGM used a 5 point knob, while the Coleman used a 12 point knob.

520 valve knobs, AGM (left), Coleman (right)

520 valve knobs, AGM (left), Coleman (right)

Frames

Spare parts tubes

There are three styles of spare parts tubes for these stoves which are held in the frames. There’s a short one which holds one vaporizer and I don’t know what else originally. It has no cap as the top of the tube is covered by the holder in the frame. These seem to be on the 1941-1943 stoves as both my 1941 AGM and my 1943 Coleman use it. The other two styles are significantly longer with one style using a slip on cap and the other using a threaded cap. They typically contain a vaporizer (with screen and cleaning tip/needle installed), On/Off valve-stem graphite packing, vaporizer tip, three vaporizer screens and a separate cleaning tip/needle.

Three styles of 520 spare parts tubes and their contents

Three styles of 520 spare parts tubes and their contents

Wrenches

It seems that only the 1944 and 1945 stoves have service wrenches which are stored in the frame using a spring-steel clip. If the earlier stoves had these I don’t know where they were kept.

Funnels

I believe that most stoves came with a funnel which was attached to the frame with a chain. The funnels are a slightly different shape for the two that I have. There must be another style, however, because the 1941-1943 Coleman stoves have a smaller fuel cap and filler opening. A lot of stoves have had parts replaced over the years and I don’t know for sure what is original, but best as I can tell, one is an AGM style and the other is for Coleman.

Two styles of 520 funnels, AGM (left), Coleman (right)

Two styles of 520 funnels, AGM (left), Coleman (right)

Gaskets and seals

If you’re planning to fire-up one of these stoves you need to check for leaks. Typical places are at the Main On/Off valve packing and nut, the fuel cap gasket, and possible at the stem cleaner packing and nut. You’ll need to pump pressure in the stove and the pump leather may be worn out or maybe it’s just dried out and needs oil. Use neatsfoot oil (baseball glove oil) to re-hydrate the leather, by applying some and letting it soak in for a bit. Then add a little more and work it in gently to the leather on both sides. If the leather is torn at all it will likely need to be replaced. These are generally available.

520 seals and gaskets, tip cleaner with packing (left), On/Off stem packing (top), pump leather (bottom), large and small fuel cap gaskets (right)

520 seals and gaskets, tip cleaner with packing (left), On/Off stem packing (top), pump leather (bottom), large and small fuel cap gaskets (right)

Leak testing

If you don’t want your stove to end up in a fireball, check for leaks before lighting. In addition to the above locations (the two graphite packings, and fuel cap gasket) you need to check the mating surface between the vaporizer and main valve body. The way I do this is to pump the stove to 20 or 30 strokes, place my finger (or rubber stopper) over the vaporizer with the tip cleaner/needle down (so you don’t poke your finger or damage the needle) and then turn on the main valve and see if fuel is leaking anywhere other than right around your finger/stopper. If it is, tighten any fittings, including the main nut holding on the vaporizer if required. Don’t light the stove until the problem is resolved.

Canister

From what I’ve seen, all AGM stoves used the two-piece canister. It appears that these were steel from 1941 through 1943 and then were aluminum for 1944 and 1945. Coleman, for years 1941-1943, used a half canister/stove cover which was held in place over the top of the stove by means of a spring-steel clip in the frame. Then, in 1944 and 1945 they switched to using the aluminum, 2-piece case. This case design was used continuously until 1987 for the M1942 and M1950 stoves.

Before and after

Here some shots of the AGM stove, before and after.

Here's the 1941 AGM as I received it

Here’s the 1941 AGM as I received it

Here's the 1941 AGM after full disassembly, cleaning and painting

Here’s the 1941 AGM after full dis-assembly, cleaning and painting

Recently, I used the 1943 Coleman 520 stove on a canoe trip for making coffee. See my previous blog post which shows the coffee percolator and stove in action.

Thanks for visiting my blog.

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