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Coming Late October
Now in final testing
The B04 is being test-run before release at the end of October. Be the first to know when it launches, and don't miss the first-batch gift.
Notify MeAir-Cooled · Hit & Miss · DIY Kit
A 1910s farm engine, built for your desk
A working miniature of the little air-cooled Chore Boy, the engine that did the chores on American farms and, under the Amanco name, on British ones too. Belt-driven fan, finned cylinder, glass drip oiler and twin spoked flywheels. Build it yourself, then hear it run.
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Before power lines reached the countryside, a small engine like this was the hardest worker on the farm. Built in the American Midwest in the 1910s, these little "chore" engines pumped water, ground feed, turned cream separators and sawed wood, day after day, for families who couldn't afford a hired hand.
They weren't fancy. They were plain, honest machines, but they started, they kept running, and they cost far less than the big engines of the day. For many families they were the first taste of mechanical power. Thousands crossed the Atlantic to work on British farms, where they earned the same loyal following.
The air-cooled versions were especially practical. With no water hopper, there was nothing to freeze in winter and less weight to carry around the yard. Cooling fins and a small belt-driven fan did the job instead.
"Pop… whoosh, whoosh… pop."
To many people, that is the sound of a grandparent's farm.
A century later, the farmers are gone but the engines are not. Collectors restore them and run them at shows, and they remain among the most collected vintage engines in the UK. The B04 brings that sound to your desk.
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A hit-and-miss engine has no throttle. When the flywheels spin fast enough, the governor holds the exhaust valve open and the engine coasts without firing. That's the "miss." As the flywheels slow, the valve closes and the engine fires again: the "hit."
The Build✦ ✦ ✦
Building the B04 is half the fun. Watch the fan drive, timing gears and ignition come together, then hear the first "pop". It's the best way to learn how an early farm engine really works.
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| Model | OKMO B04 |
|---|---|
| Engine type | Horizontal single-cylinder, 4-stroke, hit-and-miss |
| Inspired by | 1910s air-cooled Chore Boy (sold in Britain as Amanco) |
| Displacement | 3.6 cc |
| Bore × stroke | 16 mm × 19 mm |
| Speed range | 500–3,000 rpm |
| Cooling | Air-cooled: cylinder fins + belt-driven fan |
| Ignition | Mechanical contact igniter + CDI |
| Ignition power | 1 × AA 1.5V battery |
| Lubrication | Adjustable glass drip oiler + oil mixed in fuel (splash lubrication, no oil pump) |
| Fuel | Gasoline, 92/95 octane or higher |
| Engine oil | 2T or 4T engine oil, mixed into the fuel |
| Fuel-to-oil ratio | 25:1 – 30:1 |
| Starting | Flick the flywheel quickly by hand (clockwise), or use an electric drill with the starting rod |
| Power output | Belt pulley |
| Main material | CNC-machined metal |
| Dimensions | 225 × 115 × 130 mm |
| Assembly | DIY kit (assembly required) |
To thank our first-batch customers for their support, we'll include a miniature vintage-style double-wick oil lamp free with every first-batch B04. With its wire handle and twin spouts, it's a nice finishing touch for your farm-engine display. It comes in brass or black, and the color is chosen at random. Please note: it's a decorative display piece and is not meant to be lit. After the first batch, it will be sold as an optional accessory.
Also available: a vintage-style vertical water pump that runs from the B04's pulley.
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The B04 isn't on sale yet. It's currently in production and final testing, and we plan to open orders at the end of October. Production is expected to be completed and orders shipped before the end of December. Click Notify Me to be the first to know when it launches, and follow Stirlingkit for production updates.
The B04 is a modular kit, so it arrives partly assembled, and it makes a good first engine kit. Every part that needs fine adjustment is pre-assembled and adjusted at the factory, including the timing gear & governor and the cylinder head valve gear with its contact igniter. You won't have to set valve clearance or ignition timing yourself. Simply put the modules together, connect the fan drive and wiring, then add battery, fuel and oil and follow the manual for the first start. No special tools or machining skills are needed, and most builders finish in about 2 hours. Like any real engine, it may take a few tries to get the fuel setting right on the first start. That's normal, and part of the fun.
The OKMO B04 engine kit, hardwood base and assembly manual. Not included: AA battery, gasoline and engine oil.
While it runs: with no water jacket, long high-speed runs build heat, so run it in sessions and feel the cylinder temperature. The exhaust gets very hot. Run it in a ventilated space away from anything flammable. After running, top up or drain the drip oiler.
Yes. The ignition contacts are in plain view, so wear, oil build-up or a changed gap can be spotted by eye and fixed by hand.
It is a miniature inspired by the 1910s air-cooled Chore Boy (Amanco in Britain). To stay as close as possible to the original, it recreates these details:
Some details, such as the hardwood base and battery box, are designed for desktop display.
Yes. The belt pulley lets the B04 drive small accessories, such as the optional vintage-style vertical water pump.