D-400 series engine
 Restored Masport Iron Horse engine
Manufacturer Outboard Marine Corporation (OMC)
Also called Iron Horse
Production 1954--1977
Successor D-600
Configuration Single-cylinder 2-stroke
Displacement 108.99 cc (6.651 cu in)[1]
Cylinder bore 60.325 mm (2.3750 in)
Piston stroke 38.1 mm (1.50 in)
Cylinder block alloy Aluminium
Cylinder head alloy Aluminium
Compression ratio 4.5:1
Fuel system Float carburettor
Fuel type Petrol
Oil system 16:1-32:1 pre-mixed fuel:oil mix
Cooling system Air-cooled
Power output 2.6 kW (3.5 hp)[1]

The D-400 series engine or the Iron Horse engine was a light-duty 2-stroke engine used for powering lawnmowers produced in the 1960s to the early 1980s. D-400 engines were single-cylinder engines designed and manufactured by the Outboard Marine Corporation (OMC; Johnson and Evinrude) for Lawn-Boy[2] and Masport. The D-400 engines displaced 109 cc, generated 2.61 kW of power, and operated in the range of 2400-3300 RPM.[1][3] The engines have a distinctive rectangular cowling that has created a nickname of Brick-top mowers. Another distinctive feature is the two-finger vertical recoil starter.[3] The kidney-shaped muffler and exhaust unit is mounted beneath the mowers' deck and gives the engine a small, low profile design when compared to the newer and more powerful lawnmower engines. The ignition system employs a magneto, points, and a condenser (capacitor) set-up with an unusual spark-advance system which utilised a weight on the crankshaft to adjust the spark-advance amount depending on engine speed. The sprung governor was also unusual with a throw-yoke which operated under the flywheel and was linked to the throttle. The carburettor was a float design and fed into a pair of reed valves.

The D-400 engines are now a popular engine restoration job due to their distinctive shape and low cost.[4][5] Parts, however can be difficult to source and therefore multiple engines are often bought to satisfy part requirements. The recommended oil:fuel mix is either 16:1 or 32:1 depending on age.[1] In New Zealand and Australia, Masport offered the D-400 engine on their Premier, Premier II, Rancher, Rotacut, and Tornado models.[6] In the Oceania market, the D-400 was called the Iron Horse engine.

See alsoEdit


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