Sunbeam 1921 8HP 976 cc JAP 2 cyl sv 3608

Sunbeam 1921 8HP 976 cc JAP side valve V-twin frame # 83670 engine # KT/21 494

The first Sunbeam V-twin is brought out in 1914; although the company claims that the 3 ½ HP single was also capable to pull a sidecar, a special sidecar model is thought necessary to keep up with the competition. This first V-twin model is powered by a 770 cc JAP engine, for 1915 a 798 cc Abington King Dick power source is used. The following year the twin is built using the 996 cc Swiss MAG engine, while from 1917 onwards JAP is back in favour and would continue to supply their 8hp (976 cc) engines until production of Sunbeam’s V-twin models ceases in 1923. For model year 1922 Sunbeam introduces a 4 ¼ HP 599 cc single with 85 x 105 mm bore x stroke dimensions and that model will become the future sidecar machine; in 1922 the V-twin combination, albeit with a more luxurious sidecar, is almost 30% more expensive than the 4 ¼ HP combination.
As to the cubic capacity of the 8 HP JAP engine: the November 1920 Sunbeam catalogue mentions bore x stroke measurements of 85 x 85 mm, giving 996 cc. The 1920 JAP catalogue mentions 85.5 x 85 mm, 980 cc. In 1921 and 1922 Sunbeam quotes the same dimensions but comes to 986 cc. Feeding 85.5 x 85 to our calculator results in a cubic capacity of 976.05 cc, and that appears to be backed by the 1923 catalogue, that mentions 976 cc.
The 1919 and 1920 V-twins are equipped with Brampton Biflex front fork, from 1921 on a leaf spring fork is fitted: “The Sunbeam Patent leaf spring front fork gives remarkably easy steering and absorbs all road shocks. At the inner end the leaves are anchored to the lower shackle of the forks. At the outer end the two upper leaves move freely between two rollers. Side-play is impossible with this type of fork, since no wear takes place. Leaves, rollers and shackles are easily and simply lubricated.” From 1919 on an internal expanding brake is fitted to the rear wheel, which proves more effective than the earlier dummy belt rim system.
Because of their high price and relatively short production run, not many Sunbeam V-twins have survived. The Marston Sunbeam Club & Register have recorded close to 2200 surviving Sunbeams, of which 36 are V-twins and only 10 are 1921 models. see:

Model Year Matrix

The machine we present here is an older restoration. According to the accompanying V5 registration document she was first registered on August 15, 1921, to a Mr. Robert William Foster in Keighley, West Yorkshire. However, research via the Kithead Trust learned us that WY124 was first registered on August 4 of that year. The number was issued by West Riding of Yorkshire County Council to W. George Richmond, who resided at Limeburn Cottage in Killinghall, Harrogate, some 25 miles away from Keighley. The last owner – according to the V5 he was only the second registered keeper – acquired her in 1986 and rode her only briefly; she has been on display in his large Sunbeam collection for many years, so some recommissioning will be required. She is fitted with a Brooks Compensating Cantilever Spring Saddle, in 1921 available in B600 and B700 types. This is the larger B700 with saddle length of 13 inch and saddle width of 14 inch. The leg shields appear to be standard fitment on this model. She comes with Bosch magneto, B&B carb and photocopied owner’s instruction book.