The Americans were impressed with Norton's racing successes but wanted a twin that was capable of the 'ton' 100 mph (160 km/h).

The 88 Dominator was only capable of 90 mph (140 km/h) and was no match for the 650 Triumph Thunderbird and BSA Golden Flash.

[2] Hopwood had left Norton and moved to BSA where he redesigned Val Page's earlier twin to produce the 650 cc Golden Flash.

[5] Hopwood was back at Norton in 1955 and enlarged his twin engine to 600 cc to produce more power.

Fuel was fed by a single Amal Monobloc carburettor except on the 99SS where twin carbs were fitted.

[6] Primary drive was by chain to a multiplate wet clutch and was enclosed in a pressed steel chaincase.

Changes included new headlight shells, detachable embellishment panels on the petrol tank, new silencers and front hub.

The model had the option of twin Amal Monobloc carburettors, and came with polished inlet ports and a hotter camshaft that had previously been fitted to the Manxman.