Produced for nearly five decades using sidevalve engines of 633cc (1908-1947) and 596cc (1948-1954)
The Model 1 of 1908 was the first Norton to use an engine built in-house, previous models having utilized Peugeot and others. The change to chain drive came in 1915, and a dry-sump lubrication was introduced in 1931. At this point the magneto was moved from the front of the engine to the rear, for better weather protection, and the following year the exhaust was moved to the right side of the motorcycle. Also in 1932, a four-speed gearbox was offered as an option.
James Norton favoured this model, and rode a Big Four sidecar combination through South Africa during this phase of development.
In the immediate post-war years the stroke was reduced to 113mm from 120mm giving a capacity of 596cc, and along with the 16H it received a new gearbox and improved brakes. The early 50s saw a change to a dual seat, and a larger fuel tank and 8" front brake were fitted. Engine performance was also enhanced.
4 h.p.; 82x120 mm. (633 c.c.); single-cylinder four-stroke; side-by-side valves; drip feed lubrication; B. and B. carburetter; C.A.V. chain-driven magneto; two-speed Sturmey-Archer gear; all chain drive; 650x65 mm. tyres. Price £135.
As a sidecar machine the "Big Four" has a reputation second to none, and, like its 3½ h.p. relative, it is also one of the fastest machines of its type on the road. The same general lines are followed in the design, but the chain drive is totally enclosed as distinct from the 3½ h.p. model, which has a chainguard on the upper portion of the drive only. Larger tyres are also fitted to the "Big Four," and if desired 700x80 mm. tyres may be obtained as an extra.
Wide domed guards are provided, and with its enclosed drive and large rubber covered aluminium footboards, it is an all-weather mount in every respect. A model is also shown fitted with the Lucas Magdyno.
Olympia Show. The Motor Cycle, December 2nd, 1920. Page 729
A Big Four sidecar combination won the 4088 mile Maudes Trophy event. The machine was completely stock, having been assembled under the watchful eye of an ACU official, and was piloted by West Country dealer Phil Pike with Arthur Bourne as passenger. Arthur later became editor of The Motor Cycle. Mr Pike died in an air raid during WWII.
In 1928 (and possibly other years) they built the Model 17C with a 490cc sidevalve and the 633cc Model 14 with a 4-speed Norton gearbox. These were the same in most other respects to the Big Four.
From the 1928 Catalogue:
From the 1953 Catalogue:
The Big 4 is world renowned for reliability. It is built throughout of the finest materials available, and its universal success is proof of the soundness of design. The machine is ideally suited to sidecar work. The side valve engine has a capacity of 596 c.c. and a bore and stroke of 82 mm x 113 mm.