The T20 was the first six speed motorcycle to go in production in the world. It was first manufactured in 1965 ( but introduced as a 1966 model) and was produced until the end of the 1968 model year. It was superseded by an updated version which was designated the T250-1. It was a 247cc two-stroke twin with many advanced features for the time and its superb performance and reliability helped establish Suzuki's position as a major motorcycle manufacturer.
In the UK the T20 was called the 'Super Six' although in the USA the bike was designated as an X6 with the advertising department tacking on the name of "Hustler".
Advertising brochures produced by Suzuki listed the following features to be found on the new model:
- Claimed power of 29HP
- Claimed weight of 297lb (135kg)
- Racing type double leading shoe 8 inch front brake
- Aluminium alloy twin cylinder engine
- Close ratio 6-speed transmission
- Twin 24mm carburettors
- POSI-FORCE lubrication
- Air pump
- Scientifically designed quiet efficient mufflers
- Safe powerful 8 inch rear brake
- Wide type tail lamp
- Safe bright turn signal lamps
- 3 position adjustable shock absorbers
- Wide, comfortable dual seat
- 3.7 gal (14 litre) gasoline tank
- Racing type throttle
- Easy-to-read tachometer and speedometer
- Sturdy oil damped telescopic front fork
- 12 Volt fully approved lighting system
In comparison to British motorcycles at the time, this was indeed a very high specification, and the T20 model sold in thousands in many countries around the globe.
The T20 was equipped with a 247cc two-stroke powerplant, which meant that oil needed to be mixed with gasoline prior to injection into the cylinder. Simple two-stroke designs simply achieved this by requiring the user to combine oil and gas together (a solution known as pre-mix) before filling the fuel tank. However, in an advanced system like the T20, which was expected to operate for longer periods at higher RPMs, this would have been unsuitable. An excess amount of oil would be burned using pre-mix under these conditions, resulting in reduced performance and dirtier emissions, which in turn would cause the exhaust system to become laden with deposits, further reducing performance. The T20 solves this problem by incorporating a once-through oil injection system known as POSI-FORCE, which consists of an engine-driven oil pump coupled to the throttle, which is designed to provide the proper amount of oil needed at the current RPM and throttle opening. The pump draws clean oil from a separate oil tank, and pumps it through hoses into the crankcase, where it is injected into the engine from a nozzle located between the intake manifold and the cylinder. A separate oil injection point is also provided for the main bearing(s) and big end rod bearings of the crankshaft. This dual-point injection made the Posi-Force system far superior to the competitions' single point per cylinder systems. Suzuki would continue to use this system on many of their two-stroke motorcycle designs for many years.
The T20 immediately had real success on the race course in the 1960's, and many are still used to this day in Classic Racing meetings around the world. The T20 has had notable success in the Manx Grand Prix and some riders have managed to lap the famous Isle of Man course at over 100 m.p.h. on heavily modified T20s.