Practical Marriage

The beauty of the Briggs and Stratton Little Gen Set


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Small generator sets first became popular in the mid-1930s. These first generators were primarily used to recharge 6-volt wet-cell batteries to operate lights and a radio for evening entertainment on farms without electricity. Later, they would be used for many different purposes including powering independent lighting by direct connection. The gas engine washing machine was very popular in rural America by this time. Consequently, in 1937 the Briggs and Stratton Co. came up with the idea to combine a washing machine engine with a generator to do both jobs at once. At that time, their washing machine engine was known as the Model WM, so this new unit became the Model WMG and was called the "Start-Charger washer motor." Not many of these units still exist, possibly because of their location under a washing machine, although records show that 9,242 were made.

Being an avid Briggs and Stratton collector, I had been looking for generator units made by the company to add to my collection. By February 2002, I had collected a PC 100 and a PC 304 generator set when I came upon an ad on the Antique Small Engine Collectors Club website ( The ad was for a small WMG engine and generator. The seller said the generator was probably not restorable, but the engine was loose and the tag on the shroud indicated Type 20651 and serial no. 1064. He said the generator was very rusty but I made an offer for both.

I had previously found a rare copy of the operating instructions for a Start-Charger washer motor at an engine show in New York. Having studied this manual carefully, I was very excited when the box finally arrived in the mail. Unfortunately, since the generator and engine were shipped in the same box without packing, they banged together, breaking the carburetor. The shroud was badly dented, and the engine/generator base was so bent they would not align when put together.

After this initial disappointment, I went to work stripping the generator, as it seemed to be the biggest challenge. The generator casing was missing and so was the top of the circuit breaker. As a result of these missing covers, the generator's insides were very corroded, either from sitting under a washing machine for many years or perhaps being out in the elements. I checked out the armature and field coil, and as I expected both were shorted out and would need rewinding.

The original casing would have had an inside diameter of 5-1/4 inches with a 1/8-inch wall thickness. I could only find 6-inch tubing to fabricate the new casing, so I cut a section out of the side; but when I welded it back together it formed a teardrop shape. By squeezing the casing in a vice to an oval shape then welding a bead up the inside, I was able to bring it back to a proper circle that fit the field coil core perfectly. Next, I made an endplate by turning down a 1/4-inch steel plate on the lathe, then drilling cooling holes and a center hole for the bearing. An automotive frost plug was pressed backwards into this hole, then filled with two felt washers and pierced with an oil cap to make a bearing cup.

New mounting studs were made from threaded rod, and a new insulated brush mounting plate was made from a type of plastic cardboard to replace the deformed original. The brushes were in good enough shape to reuse with new springs attached. The generator went back together after some persuasion.

The motor coupling was the next challenge. The coupling consists of six studs attached to the outer facing of the engine pulley that mated with a steel disc on the armature shaft of the generator. The six holes in the disc were each lined with rubber that had badly dried out and would need to be replaced. After much thought, I came up with the idea of using rubber fuel line.

I trimmed the rubber hosing neatly to the correct length by pushing a length of hose on a steel rod and turning it in a lathe while using a sharp blade to do the cutting. The restored coupling fit together very well, even though one of the pins had previously been broken off.

Now it was time to work on the engine. It was missing the muffler, gas tank and air shield. I bought a reproduction muffler from Charles Camara of CPC Reproductions, Tiverton, R.I., and a gas tank from eBay. A parts engine provided an air shield. I went to work glass-beading all the parts of the stripped engine, lightly honing the cylinder and lapping the valves smooth again.

Before the beading started on the shroud, I hammered it back into shape. I re-aligned the engine base, which had to be straight as it was also the mounting plate for the generator. A new ignition wire, spark plug, set of piston rings and gasket set came from my own stock of parts. After I cleaned up the flywheel, I gave the magnets a zap on my magneto charger to give the engine a good hot spark. Once all the parts had a smooth coat of black paint, the engine went back together again with good compression, but it still needed a carburetor. Once again, eBay provided the part, and after a good cleaning it was mounted to the engine. The assembly was now ready to mate with the generator. This marriage went smoothly and my next step was to complete a mounting board.

My mounting boards are all made from laminated beech wood with three or four coats of marine varnish to help protect against oil and gas spills. I bored holes for mounting bolts and a large one for draining the oil. This hole was lined with a piece of copper drainpipe to prevent oil from contaminating the wood of the base. I then mounted the engine and generator together on the board. All that remained now was to complete the exterior wiring before starting the unit up. This is where I ran into another snag.

Sitting on top of the generator is a circuit breaker, which is a type of solenoid switch that prevents the battery being charged from draining back into the generator should the engine run out of gas. As with everything on this generator, it was also in sad shape, and since the cover was missing the coil required rewinding. I built a jig to rewind the coil and was all set to start when I happened to mention what I was doing to a friend, Ross Walker, who knows all about Model A Fords. He asked me why I was bothering to rewind the coil. He told me they were notorious for not working well and I should consider using a 6-volt diode instead, as they worked well for the Fords he restored. This seemed like an easier solution, so using his contact, I purchased some diodes and built one into a heat sink that would fit on the original circuit breaker base.

At this stage of the restoration in July 2005, I was attending the Niagara Antique Power Assn. Show in Sherkston, Ontario. By now, I had been working on this generator set since 2002, and I had been promising to bring it to the next show and then the next, so I finally decided to take it to this show. The problem was, I did not have the time to start it in advance. As all restorers know this is usually a bad idea, and for me this time was no exception. Everything was wired properly and the only part missing was the cover for the diode, but as you can guess, the engine would not start. It seemed to be an ignition problem. I swallowed my pride, and after the show was over I took the unit home and changed the condenser. This seemed to help but the problem turned out to be a weak coil.

So on July 16, 2005, with a new coil from the local B and S dealer installed, the 6-volt battery hooked up and using the generator as a starter motor, the engine started right up and ran smoothly. The last hurdle was the cover for the circuit breaker. I carved a wooden form and tried to create a cover with epoxy with no success. Using fiberglass cloth was also not successful, so I resorted to thin sheets of Plexiglas, which turned out very well.

I took the completed generator to the Steam-Era at Milton, Ontario, and to my surprise my "little gen set" won a prize as "Best Restored Engine Under 3-1/2 HP." The engine in this unit is rated at 2/3 HP.

Contact engine enthusiast John Cox at:
2224 Wyandotte Drive,
ONT Canada L6L 2T5;

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