I have an unidentified small air-cooled 4-cycle, single-cylinder gas engine. It is a neat upright engine, about the size of a 1920s F series Briggs & Stratton. I received the engine with no carburetor, fuel mixer/fuel tank, muffler or cooling fan. It has a small German Bosch magneto with “FB1C” on one side and “B36-228” on the other. The magneto is driven directly by the crankshaft and the best part is it works well. A grooved pulley on the crank shaft has a notch cut into it for rope starting. It has three round steel pegs protruding, which I presume is part of a flexible coupling. It looks to be original.
I had a stuck and rusty Briggs & Stratton from which I took the fuel mixer and muffler and added to my little engine. I made a throttle control lever out of a piece of flat 1/8-inch-thick steel. The little engine has no governor on it, which let me control the engine speed. The spark plug is a Champion brand #31 with 1/2-inch pipe thread as on a Model T Ford car. It still works!
The brass oil filler and breather for the crank case are my doing. I made a cooling fan from a piece of 14-gauge steel, drew a CAD drawing of what I wanted, and had a metal shop technician cut it out. I have an Ideal gas engine that has a similar fan. I down-sized to get the size I needed. The fan pulley is made from a piece of 1-3/4-inch round aluminum stock. The drive belt it is an O-ring from a car automatic transmission (I work in automotive).
Because this is a fun hobby, I took a Log Cabin syrup can and used it for a fuel tank. The engine is overhead valve with the exhaust valve driven by a cam, a rocker arm and a push rod. The intake valve is naturally aspirated. The intake and exhaust valves are on opposite sides of the head for good air flow. Most engines today have both ports together for all weather operation. This engine was most likely not used in cold weather. All the bolts and nuts are cut using standard U.S. threads. All the parts are cast iron. I have not done any painting yet and don’t know if I will.
Inside the engine are two flywheels, much like a Harley-Davidson motorcycle. The circular crankcase suggests motorcycle use, however, the flat mounts on the crankcase bottom suggests otherwise. Further research suggests it was used on a small skiff or boat.
My engine runs nicely, it’s smooth and quiet and sounds like a Briggs & Stratton. I would like more information on this engine so I can answer questions when it’s on display.
If you have any information on Dave’s mystery engine, send details to editor@gasenginemagazine.com. Details will be shared in a future Flywheel Forum.
Originally published as “Unidentified Upright” in the June/July 2023 issue of Gas Engine Magazine.
59/1/1: Unidentified Upright Letter Response
The following letters are in response to the article Unidentified Upright, June/July 2023 issue of GEM by Dave Irey.
Dave’s mystery engine is a Mar-Tan, built around 1929. Most of these engines were used on Moto-Mower Jr. lawn mowers. Not sure what Dave’s engine powered with that three-pinned drive coupling. There should be a drip oiler where the brass oil cup is. The original carburetor was likely a Tillotson MS5A model. Here are photos of an original engine I have, and the original mower literature.
Mike Stockard, via email
The engine is a Mar-Tan. I have the same engine with a slightly different mounting. I took it off a Mar-Tan mower. It was a self-propelled oscillating type mower.
Dan Baalman, via email
