Sunbeam Motorcycles

Sunbeam Models for 1920/1921

Olympia Show 1920

SUNBEAM. (Stand 129.)

  • 3½ h.p.; 85x88 mm. (499 c.c.); single-cylinder four-stroke; side-by-side valves; drip feed lubrication; Amac or B. and B. carburetter; chain-driven magneto; three-speed constant mesh type gear; enclosed chain drive; Dunlop or Bates ,650 x 65 mm. tyres. Price £155 8s.

John Marston, Ltd., Sunbeamland, Wolverhampton.

Although the capacity of the Sunbeam single-cylinder engine is only 499 c.c, it has proved capable of the severest sidecar work, and for dual purposes it stands in the highest rank. Famous long ago on Sunbeam pedal cycles, the oil bath gear case forms the most prominent feature, although the three-speed gear box is also a very fine piece of work. Of course, the rear wheel is instantly detachable without disturbing the drive or gear cases in any way. Laminated front springing was first adopted on this model, last year, and is retained both in standard and in T.T. version, the latter differing only in the substitution of dropped bars and foot-rests. This T.T. machine must not be confused with Messrs. John Marston's commendable attempt to provide a really fast and light solo mount, not dissimilar to the machine which won the 1920 Senior T.T. In this machine weight has been sliced off wholesale, leaving only those features which will delight the heart of the speedy soloist. Parallel link forks, a lighter gear box without kick starter, simpler braking on dummy belt rims, all contribute to the good cause of decreased weight; while a special aluminium piston should mean increased efficiency. The transmission system is unaltered, and the sporting Sunbeam is priced at £152 5s.

  • 8 h.p. J.A.P.; 85.5x85 mm. (976 c.c.); V twin cylinder four-stroke; side-by-side valves; drip-feed lubrication; Amac or B. and B. carburetter; chain-driven magneto; three-speed constant-mesh type gear; enclosed chain drive; Dunlop 650x55 mm. tyres. Price with sidecar £237 6s.

For those who desire a great reserve of power for really heavy passenger work the well-known J.A.P. engined outfit is still a centre of attraction. Following very closely the general lines of the smaller touring machine, it holds an enviable position in its class, and for 1921 has not been altered. Large mudshields and the new Brooks cantilever saddle are fitted.

Olympia Show, 1920
The Motor Cycle, December 2nd, 1920.

Sunbeam 1920-1921 Models

1920 Models

The three model range from 1919 continued with minor variations to the 3½ h.p. models.

A new, Marston patented, leaf spring suspension was introduced for the front forks of the 3½ h.p. models along with a rear drum brake. The front wheel retained a bicycle-style stirrup brake.

The 3½ h.p 'Sporting Model' was differentiated by lower handlebars, footrests rather than footboards, and a higher compression engine.

The magneto drive cover assumed what was to become its traditional lozenge shape. The engine was given larger cooling fins.

The range for 1920 consisted of:

2¾ h.p. Standard model
2¾ Sporting model
8 h.p. 996cc JAP V-twin model

An advertisement for the 1920 models reads:

THE SUNBEAM

with Patent Enclosed Oil Bathed Chain Transmission is in a class of its own and can be ridden in all weathers.

The Design. Workmanship. and Finish, are also superior to anything on the market.

Its outstanding features are.:-
1. The Sunbeam Patent Front Fork with Leaf Spring
2.The quick detachable and interchangeable Wheels.
3.The internal expanding Brake on Rear Wheel.
4.The large Tank.
5.The splendid Mudguarding.
6.The All Black Weatherproof finish.


Sunbeam 1921 Models

A third version of the 3½ h.p. model was available along with the 'Standard' and 'Semi-Sporting' models which were little-changed from their 1920 versions. The new 'Sporting Solo T.T. Model' reflected Thomas Corbett de la Hay's Senior T.T. win the previous year.

Cycle Parts

The Marston patented, leaf spring suspension was introduced for the front forks of the 8 h.p. v-twin model to become standard for the range except for the T.T. model which had Marston-made Druid style front forks.

The T.T. model had 'vee' rim brakes with a Ferodo-lined shoe at front and back, whilst other models retained a bicycle style stirrup brake at the front and drum brake at the rear.

Engine and Gearbox

A high compression engine remained available for the Semi-Sporting model, and a higher compression, finely tuned sports engine for the T.T. model.

The T.T. model also had a smaller and lighter three-speed gearbox with 'crash' sliding pinions rather than the constant mesh 'rack and pinion' earlier gearbox. The 'crash' gearbox was to become the standard Sunbeam gearbox.

The range for 1921 consisted of:

3½ h.p. Standard model

Engine
Cylinder capacity: 499cc
Bore x stroke: 85mm x 88mm

Frame numbers:
From 10000 (1920) to 12600

Engine numbers:
From 9000 (1920) to 11599

Price: 148 guineas

3½ h.p. Semi-Sporting model

3½ h.p. Sporting Solo T.T. model

Engine
Cylinder capacity: 499cc
Bore x stroke: 85mm x 88mm

Frame numbers:
From 10000 (1920) to 12600

Engine numbers:
From 9000 (1920) to 11599

Price: 145 guineas

8 h.p. 996cc JAP V-twin model

Engine
Cylinder capacity: 996cc
Bore x stroke: 85mm x 85mm

Frame numbers: 83501 up
Engine numbers: 72000 up

Price: 176 guineas

Source: sunbeamsidevalve.com