Johnson Iron Horse

Listed below are the various models of the Iron Horse and some data regarding them.
Model Carburetor Type Cycle Bore Stroke Gas
Tank Capacity
R.P.M. Horsepower
(Source: Some of the data are from “Johnson 4-Cycle Iron Horse Manual”)
X-400 Suction-Feed 1 2-1/8″ 1-3/4″ 3 qt. 1800 5/8
X-400 Down-Draft 1 2-1/8″ 1-3/4″ 3 qt. 1900 3/4
X-500 Down-Draft 1 2-1/4″ 1-3/4″ 3 qt. 2000 1
Johnson Iron Horse

Johnson Iron Horse


These engines were designed for washing machines, lawn mowers, small automobiles, lighting plants pumps, and numerous other machines. The angle cylinder permits low height for engine mounting in close quarters and for keeping the center of gravity low. The engine’s adaptability to numerous installations is made possible by a wide variation in equipment, e.g.,  foot-pedal, rope and hand start.

The regular gasoline tank for the suction-feed engine has a one-quart capacity; however, other tanks of special dimensions could be use on the engine. A one-gallon cast-iron tank could also serve as a substantial tank. On the engines with the down-draft float-feed carburetors, an overhead tank could be mounted on the engine, or some other gravity arrangement could be used. The exhaust outlets also may be modified, and a special screen for the air intake to flywheel-fan was available for the engines.

On some generator-set applications, shielding of ignition was required. Belt or direct drive could be taken from either end of the crankshaft. Iron Horse engines are regularly equipped with a V-belt pulley on each side ( pulleys in various sizes). A dry-type air filter could be used on the suction-fed carburetor intake, while the oil-bath type were used on the down-draft float-fed X-500 engine.


The engine operates on a four-stroke-cycle principal requiring four strokes of the piston to complete the event of the cycle of intake, compression, power, and exhaust. Two poppet valves (intake and exhaust) allow the admission of fresh fuel changes, while discharge of the burned gases is by way of the two valves. The intake and exhaust, which operate by cams, are timed close at predetermined positions of the piston.


Lubrication is by the splash system from the crankcase, with a splash arm on the connecting rod. The crankcase’s oil capacity is 3/4 pint. The regular gasoline tank with suction-fed carburetor has a one-quart capacity, while the overhead gravity-fed tank’s capacity is three quarts. The base gasoline tank’s capacity is two quarts.


  1. Be sure engine crankcase is filled with oil.
  2. Fill gas tank with regular-grade gasoline. Do not use high-grade gasoline.
  3. Pull up on choke button. Do not use choke to start when engine is warm unless necessary.
  4. Step firmly (do not stomp) on starting pedal. Engine should start on two or three cranking efforts when cold if choked properly.
  5. Push choke button in gradually upon to start the engine.
  6. To stop, Pull-up on the choke button.


Spark Plug: 14 mm., 3/8 Champion, J8

Governor — Mechanical fly-ball type mounted on crankshaft inside crankcase. Close speed control.  Speed adjustment