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A hopper-cooled farm engine of the 1910s and 1920s, made again in miniature, and it runs.
POP… whoosh… whoosh… whoosh… POP
Pre-order price: $399.99 $499.99
$100 off, applied automatically at checkout. No code needed.
Reserve yours now and it will be among the first to leave the workshop. We will email you as soon as your engine ships.
You know that sound. Maybe it came from the pump house on your grandfather's farm. Maybe you heard it for the first time walking the rows at an engine show, and stopped, and stayed longer than you meant to.
The B03 brings that sound home. Flip the flywheel, hear it catch, and watch the governor take over: one hit, then the flywheels coast on their own weight while the exhaust is held open, then the latch drops and it fires again. Nothing about it is simulated. It is the same mechanism that kept water flowing on farms a hundred years ago.
Turn the sound up. That rhythm is the governor at work.
A flip of the flywheel, a cough, then a clean pop as it fires on its own. That moment never gets old.
The flyweights swing out, the latch catches, and the engine starts to coast between hits. Adjust it, and you set the rhythm yourself.
On a long run the water in the open hopper begins to warm and steam, cooling the cylinder exactly the way the originals did.
Warm oil, a hint of gasoline, the drip oiler ticking away. A real engine, doing real work, right in front of you.
Look closely and you will find the Hired Man in every part of the B03: the proportions, the hopper, the flywheels, the brasswork. It is made for collectors who know these engines well, and who appreciate one that is done right.
The exposed crank, connecting rod and side shaft, just as on the farm engines of the era.
The tall hopper over the cylinder, the defining shape of a hopper-cooled engine, and it really cools by evaporation.
Heavy spoked flywheels with polished rims, finished in classic scarlet.
Flyweights, latch and exhaust pushrod all in view, doing exactly the job they did on the full-size engine.
A glass-and-brass drip oiler and brass fittings, the small details a collector notices first.
Hardwood skids and a dovetailed battery box, set up the way engines are displayed at a show.
A farm engine was never meant to sit still. It rode on a cart and went wherever the work was, and that is how the best engines are still shown today. Add the ST-02 and your Hired Man becomes the complete outfit.
$100 off the engine, applied automatically at checkout.
Arrives fully assembled on its wooden base. Add one AA battery, fuel mix, water and oil, then start it by hand or with a drill.
No hard pull, no cranking. A light flip of the flywheel starts it, and if you would rather not, a household cordless drill spins it up just as well.
Precision CNC aluminum alloy body, brass fittings and stainless steel flywheels, made for repeated running and years on display.
Questions before or after you buy? Email our team at service@stirlingkit.com and we will walk you through it, step by step.
| Model | RETROL & OKMO B03 (Red) |
|---|---|
| Prototype | "Hired Man" hopper-cooled farm engine |
| Scale | 1/4 |
| Form | Ready to Run (RTR) |
| Engine Type | Gasoline, horizontal single cylinder, four-stroke |
| Displacement | 3.6 cc |
| Bore × Stroke | 16.0 × 19.0 mm |
| Speed Range | 500–3000 rpm |
| Governor | Centrifugal flyweight, hit-and-miss (exhaust latch-out) |
| Cooling | Evaporative hopper water cooling |
| Lubrication | Fuel-oil mix with brass drip oiler |
| Fuel Mix Ratio | 25:1 to 30:1 (gasoline : oil) |
| Recommended Fuel | Regular unleaded gasoline, US 87 / RON 92 or higher |
| Recommended Oil | 2T/4T 10W-50 engine oil |
| Ignition | Spark plug with igniter, triggered mechanically (igniter included) |
| Ignition Power | 1 × AA 1.5V battery (not included) |
| Spark Plug | 3/16-40 imperial thread (included) |
| Starting | Hand start by flywheel, or drill start |
| Materials | Aluminum alloy, brass, stainless steel, wood |
| Color | Red |
| Product Size | 22.5 × 11.5 × 13 cm (8.9 × 4.5 × 5.1 in) |
| Product Weight | 1650 g (3.6 lb) |
| Package Size | 27 × 16 × 18 cm (10.6 × 6.3 × 7.1 in) |
| Package Weight | 1750 g (3.9 lb) |
| Packaging | Printed gift box |
| Age | 16+ |
Yes. The B03's centrifugal governor physically latches the exhaust valve open above set speed, so the engine skips firing and coasts until it slows down. The rhythm you hear comes from the mechanism itself, not from electronics.
No. The B03 is supplied ready to run. Add a AA battery, fuel mix, water in the hopper and oil, and it is ready to start.
The B03 is hopper water-cooled and pays tribute to the Hired Man. The B04 is air-cooled, with cooling fins and a fan, and pays tribute to the Hired Hand, the air-cooled brother of the Hired Man. Side by side, they make a fine pair.
Yes. The ST-02 Steerable Engine Cart bolts beneath the B03's wooden base, with metal six-spoke wheels, a working steering front axle and a wooden pull tongue. It turns the B03 into a complete, show-style outfit. Sold separately.
It runs on gasoline and produces exhaust, so we recommend running it outdoors or in a well-ventilated workshop. As a display piece, it is perfectly at home indoors.
B03 Hired Man (pre-order)
B04 Hired Hand (pre-order)$100 off each engine, applied automatically at checkout.
Some engines you restore. Some you inherit. This one you can simply start.
