norton continued production of their 3.5 hp and big 4 singles well into the war period, though in november 1916 the ministry of munitions issued an order that no further work on motor cycles or cars would be allowed from 15 november 1916 without a permit. by this time most motor cycle companies were already either producing munitions (or aircraft parts), or devoted to the export trade. norton were involved in exporting and earlier that year had announced a new 'colonial model' of their 633cc big 4. this featured an increase in ground clearance from 4.25" to 6.5", by altering the frame, larger tank, greater clearance on mudguards, and a sturdy rear carrier. the engine was unaltered, and transmission was via a sturmey-archer 3-speed gearbox.