Engine and transmission

The 597 cc engine was enlarged from the 88's 500 cc engine by increasing the bore and stroke from 66 mm (2.6 in) x 72.6 mm (2.86 in) to 68 mm (2.7 in) x 82 mm (3.2 in).^[3] The pre-unit 360° pushrod vertical twin used cast iron cylinders and an alloy cylinder head with a 7.6:1 compression ratio. Fuel was fed by a single Amal Monobloc carburettor except on the 99SS where twin carbs were fitted.^[2]

Ignition was from a Lucas magneto and the power for the lights was from a dynamo. In 1958 this was changed to coil ignition and a crankshaft mounted alternator.^[2] The model reverted to a magnito in 1962.^[6]

Primary drive was by chain to a multiplate wet clutch and was enclosed in a pressed steel chaincase. The gearbox had 4 speeds.^[2] For the 1957 model the gearbox was changed to the AMC gearbox used on AJS and Matchless twins.^[7]

Cycle parts

Cycle parts were shared with the 88. The frame was the featherbed and forks were short Roadholders. Full width alloy hubs were fitted with drum brakes, 8 in (200 mm) at the front and 7 in (180 mm) rear. A 7 in (180 mm) headlight was fitted with the speedo, ammeter and switch mounted in its shell.^[2][8]

The featherbed frame was modified in 1960 by moving the top tubes closer together. The updated frame came to be known as the 'slimline' and the previous version as the 'wideline'.^[9][10]

99

1959 Dominator 99 'Smooth-Look'

The Model 99 was introduced in 1956. Norton updated their range, including the 99, to their new 'Smooth-Look'. Changes included new headlight shells, detachable embellishment panels on the petrol tank, new silencers and front hub.^[11] A redesigned cylinder head was also fitted.^[3] The Dominator name was revived in 1959 and the model was called the Model 99 Dominator.^[12] With the introduction of the 'Bodystyled' Deluxe model, the existing bike became the 88 Standard Dominator.^[13] The model was discontinued in 1962 following the introduction of the 650 cc Dominators.^[14]

99 De Luxe

Norton had first introduced semi-enclosed bodywork in 1958 on the 250 cc Norton Jubilee.^[14] The 'Bodystyled' semi-enclosed bodywork was offered as an option on the Dominators in 1960, the De Luxe models.^[13][14] Intended as a tourer, the semi-enclosed bodywork was claimed to keep the rider cleaner and the bodywork was easier to clean than a bare design. A fairing was offered as an optional extra. Many of these models later had the bodywork stripped off to convert the bike to a cafe racer. The model was discontinued in 1962.^[14]

99 Sports Special

The 99 Sports Special Dominator (99SS) was introduced in 1961 as a higher performance version of the 99. 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. A siamesed exhaust was fitted, or the option of a dual system and the option of chrome mudguards. Motor Cycle magazine obtained a top speed of 108 mph (174 km/h) during a test of the 99SS. The model was dropped after only a year when the 650SS was introduced in 1962.^[15][16]

Bibliography

• Clayton, Graham (1 August 2012). "Vintage Norton 99 Deluxe Motorcycle from the 1950's". Motorcycle Mojo. Retrieved 29 June 2021.
• Hewitt, Sam (1 October 2018). "Norton Dominator Model 99". Classic Bike Guide. Retrieved 27 June 2021.
• Kemp, Andrew (2000). The encyclopedia of classic British bikes. Enderby, England: Abbeydale Press. ISBN 978-1-86147-058-4.
• Reynolds, Jim (1990). Best of British bikes. Patrick Stephens. ISBN 978-1-85260-033-4.
• Salvadori, Clement (6 March 2019). "Retrospective: 1956-1962 Norton Dominator 99 | Rider Magazine". ridermagazine.com. Retrieved 27 June 2021.
• Sharkey, Alex (19 March 2021). Classic Bikes: Essential Transport. Character-19.
• "Norton "Two Group" Program For 1956". American Motorcyclist. December 1955. p. 24.