Unapproachable: The 1957 Norton International Model 30

The Norton International Model 30 with its Featherbed frame epitomizes British bikes.

| July/August 2015

Top speed: 100mph-plus (est.)
490cc air-cooled OHC single, 79mm x 100mm bore and stroke, 29.5hp @ 5,500rpm (claimed)
Weight (wet):
380lb (173kg)
Fuel capacity:
4.5gal U.S. (17ltr)
Price then/now:
$750 (est.)/$7,000-$16,000

As early as 1908, Norton had adopted the famous “Unapproachable” tag line to describes its motorcycles; the slogan took on renewed meaning in 1927, when Norton’s Walter Moore designed a new overhead camshaft engine called the CS1 — for Camshaft Model One.

Based on the bottom half of Norton’s Model 18 overhead valve 500cc single, an engine first seen in 1922, the rest of the CS1 was completely different, with a vertical bevel-shaft drive to an overhead camshaft. The bevel tunnel and the paddle-shaped timing chest and cover on the right side of the crankcase gave the appearance of a cricket bat, a reference used by British enthusiasts to this day.

Placed in a new frame complete with a Webb girder fork, a purposeful-looking gas tank and 8-inch drum brakes front and rear, the CS1 looked and acted the business of racing. And while the engine wasn’t entirely without faults, the machine performed admirably. Alec Bennett took a new CS1 to victory in the 1927 Isle of Man Senior TT, ensuring the importance of the overhead cam engine in Norton’s racing program.

In 1929, Moore — who owned the rights to the overhead cam engine — left Norton to pursue a career at German-based NSU. Because of this move, Norton was prompted to redesign the overhead cam engine. Chief designer Arthur Carroll led the work, together with assistant Edgar Franks and development engineer Joe Craig.

Gone was the cricket bat-shaped tower drive, but Carroll retained the CS1’s 79mm bore by 100mm stroke, and these dimensions remained the same for every 500cc single Norton made until 1963.

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