Classic Bikes Custom Bikes Individual Racing Bikes AJP AJS Aprilia Ariel Avinton / Wakan Bajaj Benelli Beta Bimota BMW Brough Superior BRP Cam-Am BSA Buell / EBR Bultaco Cagiva Campagna CCM CF Moto Combat Motors Derbi Deus Ducati Excelsior GASGAS Ghezzi Brian Gilera GIMA Harley Davidson Hero Highland Honda Horex Husaberg Husqvarna Hyosung Indian Jawa Kawasaki KTM KYMCO Laverda Lazareth Magni Maico Mash Matchless Mondial Moto Guzzi Moto Morini MV Agusta MZ / MuZ NCR Norton NSU Paton Peugeot Piaggio Revival Cycles Roland Sands Royal Enfield Sachs Sherco Sunbeam Suzuki SWM SYM Triumph TVS Ural Velocette Vespa Victory Vincent VOR Voxan Vyrus Walt Siegl Walz Wrenchmonkees Wunderlich XTR / Radical Yamaha Zero Video Technical
Complete Manufacturer List

Sunbeam Model 6

Make Model.	Sunbeam Model 6 "Lion"
Year	1921 - 37
Engine	Single cylinder, side valve
Capacity	492 cc / 30.0 cu in
Bore x Stroke	77 x 105.5 mm
Cooling System	Air cooled
Compression Ratio	5.0:1
Exhaust	Single
Starting	Kick
Power	3.4 kW / 4.5 hp
Transmission	3-Speed wide ratio
Final Drive	Chain
Gear Ratios	1st 13.7 / 2nd 8.2 / 3rd 4.9:1 (Side car model: 1st 14.6 / 2nd 8.7 / 3rd 5.25:1 or 15.5, 9.3 and 5.6)
Frame	Single downtube cradle
Front Suspension	Druid forks
Rear Suspension	Rigid, spring loaded saddle
Front Brakes	Drum
Rear Brakes	Drum
Wheels	Steel, laced wire spokes
Tyres, Front and Rear	3.25 x 26" (Optional: 3.50 x 26")
Dimensions	Length: 2083 mm / 82" Width 813 mm / 32"
Wheelbase	1359 mm / 53.5"
Saddle Height	711 mm / 28"
Dry Weight	136 kg / 300 lbs
Fuel Capacity	11.4 L / 2.5 Imp gal / 3.0 US gal
Oil Capacity	2.3 L / 4.0 Imp pt / 4.8 US pt
Source	Sunbeamsidevalve.com

The 1921 French Grand Prix proved a successful testing ground for Marston's prototype, long-stroked engine of 492cc. It had a 77mm bore by 105.5 mm stroke. The 'Longstroke' model went into production the following year, winning the Senior T.T. It was the last side-valve engined motorcycle to do so.

The Sunbeam Longstroke was the fastest production, single cylinder, side-valve motorcycle in its day. The model stayed in production for the life of the company and the subsequent AMC take-over in late 1937. It underwent many stylistic changes; notably from flat tank to saddle tank in 1929. Known as the Model 6 prior to ICI's takeover of the company in 1929, it was marketed as 'the Lion' during the 1930s - the tank emblazoned with ICI's trademark lion emblem.