Sunbeam Model 8



Make Model.

Sunbeam Model 8


1924 - 31


Single cylinder, OHV


347 cc / 21.2 cu in
Bore x Stroke 70 x 90 mm
Cooling System Air cooled
Lubrication Dry sump
Induction AMAC carburettor
Exhaust Single


Power 2.1 kW / 2.75 hp
Transmission 3-Speed 
Final Drive Chain 
Frame Bifurcated front down tube

Front Suspension

Druid forks

Rear Suspension

Rigid, spring loaded saddle

Front Brakes

Drum, internal expanding

Rear Brakes

Drum, internal expanding
Wheels Steel, laced wire spokes
Source Marston-Sunbeam

1924 was a year of firsts for the Sunbeam. It was the year the now familiar model number system was introduced, and it was on the new overhead-valve models 8, 9, 10 and 11 that most of the new features were to be found.

The 1924 OHV Model 8 featured overhead valves for the first time on a Sunbeam. These were controlled by triple return springs.

An EIC magneto was fitted, and an AMAC carburettor. Engine lubrication was by the Sunbeam-patented fully enclosed automatic dry-sump system. The standard fuel tank also had an oil compartment, but an optional separate oil tank could be ordered, giving increased petrol capacity.

A special detachable aluminium silencer could be ordered. To enable the cylinder head to be removed without taking the engine out of the frame, the tank tube, complete with tank, could be detached by undoing two bolts, and to accommodate the straight-through single port head, the frame featured a bifurcated front down-tube. Marstons called this a “Duplex Frame”! How seriously these two “improvements” compromised the stiffness of the frame can hardly be imagined.

This Model 8 also featured, again for the first time on a Sunbeam, internal-expanding brakes, front and rear. The v-twins had ie rear brakes from 1914 onwards, and they were also worn by the touring 3 ½ and 4 ¼ HP/Model 7s but never on the front. The more sporting models retained belt-rim brakes front and rear right up until 1924. The front chaincase was fully enclosed, as with all other Sunbeam models, but a kick-starter could not be fitted.