Late in 1916 Fuller & Johnson introduced a replacement for the model N kerosene engine.  The new engines were throttle governed and came with the equipment needed to burn gasoline, kerosene, naphtha, motor spirits, distillate and other low grade fuels.  Like many throttle governed engines of the time, they were started on gasoline and brought to operating temperature before switching to another fuel.  The large mixer contained the gasoline reservoir, needle valves, water injection feed, auxiliary air intake valve and hot air intake.  The main fuel tank was located in the hollow base.  Model K engines shared many parts with the model N.  The base, cylinder, flywheels (except 3hp) crankshaft, head, gears and other small parts were all interchangeable between the two models.  Only the related governor/mixer parts were strictly for the K.

    When the model N gave way to the NB, so too did the model K.  Debuted in late 1923 under the new designation of KA, these engines were the first to have a magneto as standard equipment.  Later on in 1924 the Wico EK and sparkplug was made available and the ignitor remained available as a special order item.  The KA often had a late style cylinder, with a different top and re-located drip oilier.  The position of the fuel tank filler on the 3 and 5 hp engines was changed as well.  Flywheels now had a wide face that was crowned to allow them to be used as a large pulley.  The KA was available in the same sizes as the K however, by 1928 the 9 and 12 hp engines were not listed in catalogs.

    The final throttle governed engine built by Fuller & Johnson was the NK.  This engine was merely an ND with throttling governor and related equipment to burn low grade fuel.  First introduced in 1930, they were built in 2, 2 1/2 and 3 1/2 hp.  Very few engines were made, making them the rarest of the rare in the throttle governed family built by Fuller & Johnson.