1928 Sunbeam 350cc Model 8
Registration no. PP 7991
Frame no. C1391
Engine no. 273/23250
Sunbeam had begun experimenting with overhead valves on their factory racers in the early 1920s and these duly appeared on production models in 1924. The new 500 roadster was known as the Model 9 while its race bike counterpart, which could top 90mph, was accordingly designated the Model 90. The 350cc versions were the Model 8 and Model 80 respectively. The John Greenwood design was advanced for its day, with a specification which included a crankshaft supported by three ball-bearings, dry-sump lubrication, and primary drive enclosed in an cast alloy chaincase. Power was transmitted by single-row chain to a three-speed, 'cross-over drive' gearbox with offside power take off.
The overhead-valve models frame and cycle parts, which had much in common with those of Sunbeam's larger side-valve models, evolved slowly. Sunbeam missed the industry's virtually wholesale switch from flat-tank to saddle-tank frames for the 1928 season, and a saddle-tank version of the Models 8 and 9 did not appear until September of that year. Changes to the overhead-valve engine were confined mainly to its top-end. The early flat-tankers featured a straight-ahead exhaust port, a peculiarity which necessitated the adoption of a bifurcated down-tube. Later on in the 1920s Sunbeam followed the then-fashionable trend to twin-port 'heads before reverting to a single-port design. Pushrod enclosure had arrived by 1930 to be followed a couple of years later by partial enclosure of the rocker gear.
The Model 8 offered here dates from 1928, the last year of the flat tank Sunbeams, and has the revised lubrication system introduced that year, which featured a Sunbeam mechanical oil pump inside a shallow bulge on the timing case. In previous years an external Best & Lloyd pump had been employed. An older restoration (believed circa 1990), the machine is presented in generally very good condition and has been test ridden recently. The accompanying old-style Swansea V5 records one Ian Young of Marcham, Oxfordshire as previous owner while the registered keeper listed, Clive Beal of Chideock, Somerset, appears to have owned it for some 30 years. It should be noted that the engine number is that of a 350cc sidevalve, it being not at all unusual for these crankcases to be substituted for a damaged OHV set.