Sunbeam 1927 3½hp Model 6 Longstroke 492 cc 1 cyl sv 3608

Sunbeam 1927 3½hp Model 6 ‘Longstroke’ 492 cc side valve frame # B1730 engine # J1778

After the Great War, Sunbeams first new design was a side valve of 77mm bore and 105.5mm stroke and a cubic capacity of 492 cc. At the works it was known as the ‘Longstroke’ to differentiate it from its short-stroke 85 mm x 88 mm ( 499 cc) predecessor. The new engine made a fantastic impression at the 1921 French Grand Prix on July, 24 at the Circuit de la Sarthe near Le Mans. The circuit length was about 17 km and the machines in the 250, 350 and 500cc classes, more than 40 in all, started at the same time. The 500cc class had 26 competitors who had to do 18 laps and from lap three Sunbeam riders Alec Bennett and Tommy de la Hay were firmly in the lead. Bennet won with an average speed of 59.9 mph (more than 95 kmh), 2 minutes in front of de la Haye. For the 1922 model year a sports machine based on this successful racer was available to the public with model designation “TT Sporting Model”. This model name was continued for 1923 and when Sunbeam started to number its model for the 1924 season, the Longstroke was christened “Model 6”. It was a light machine with narrow 6- inch mudguards, narrow wheels and without luggage rack. For 1927 Sunbeam offered two models with the Longstroke engine. Model 5 , named “Light Tourist” had footboards and oil bath rear chain case, and Model 6 kept the Longstroke name but was fitted with footrests and chain guard. Compared to the 1926 model the Longstroke now got wider mudguards and was fitted with the sturdier 1927 front forks with stronger brake anchorage and luggage rack with two leather-fronted toolboxes. Most 1927 models got wired-on wheels with 27 x 2.75 Dunlop tyres. The remarkable Longstroke engine was produced right up to 1940, fitted to the Lion Longstoke model.
The 1927 catalogue description of the Longstroke: “This machine is famous all over the world for its high speed and magnificent acceleration. It is the fasted side-valve motorcycle supplied as standard to the public. It is the ideal machine for those who require an undoubted “thoroughbred” for high speed long distance riding, but it is also extremely tractable and can be ridden in any traffic.” Titch Allen tested a 1927 Longstroke in “The First Vintage Roadtest Journal”. A quote: “When warm it will tick over so slowly that apart from counting the revolutions you can follow the four stroke cycle by watching the valves rise and fall and listen for the hiss of mixture going in and the plonk as it comes out. Plonk is the word to describe the sound of a longstroke’s exhaust and its road manners. If you want to do a feetup figure-of-eight, or win a gymkhana slow-race, the Sunbeam is the job. But it’s a Jekyll and Hyde because it will rev as well. The plonk exhaust note turns into a crackle…still mellow as benefits the character of the machine, but purposeful. In fact, the longstroke ‘Beam was the equal of most of its ohv contemporaries in performance, and ahead in reliability and good manners.”
The Longstroke we present here was first registered on August 11, 1927 and has been in the possession of the former owner for more than forty years. She is in well-used condition and appears to have been off the road for many years; a 2005 tax disc suggests she was last used on the road during that time. She comes with a buff continuation logbook showing all owners from 1949 on, and various other registration and MOT papers plus a 1927 Sunbeam Motorcycles price list for spare parts. The machine is fitted with beaded edge wheels and 26 x 3 tyres, as used in 1926, probably fitted a long time ago because of the difficulty in obtaining the rare 27 x 2.75 tyres. The machine is running but will benefit from some recommissioning. She comes with adjustable handlebars, Lycett saddle, Lucas acetylene front lamp and generator, BTH magneto, AMAC carburettor and Birmingham-made “Hercules” tyre pump.