Shrinking an engine does not shrink the physics. The OKMO D Type is a running quarter scale tribute to the Lister D, the single flywheel stationary engine built at Dursley from 1926 until 1964 in numbers exceeding 250,000. The original produced 2 horsepower at 1000 rpm from 347cc, with a 3 inch bore, a 3 inch stroke, a compression ratio near 5 to 1 and roughly 135kg of cast iron. It pumped water, milled grain and ran lighting plants in places the grid had never reached. The model reproduces that architecture and still has to run. - 16mm bore, 18mm stroke, 3.6cc, four stroke, single cylinder - 500 to 3000 rpm, around 0.2 metric horsepower - Evaporative hopper cooling, no pump and no fan - Splash lubrication from a 25:1 to 30:1 petrol and oil premix - Mechanical trigger ignition fired from a single 1.5V cell - Imperial 3/16-40 threaded spark plug The detail worth studying is the gear chest. A skew gear pair takes drive off the crankshaft and turns it through ninety degrees to spin th...