The A7 Avenger is a Kawasaki

motorcycle A motorcycle (motorbike, bike; uni (if one-wheeled); trike (if three-wheeled); quad (if four-wheeled)) is a lightweight private 1-to-2 passenger personal motor vehicle Steering, steered by a Motorcycle handlebar, handlebar from a saddle-style ...

sold 1967 through 1971.

Development

Kawasaki is the last of the big four Japanese manufacturers to start making motorcycles. In 1960, it bought a share in the

Meguro motorcycle Meguro motorcycles were built by Meguro Manufacturing Co motorcycle works (目黒製作所), founded by Nobuji Murata and a high-ranking naval officer, Takaji Suzuki, in 1937. One of the first Japanese motorcycle companies, it became a partner of ...

company that since the 1930s had made four-stroke singles up to 500 cc and later twins up to 650 cc for the Japanese and south-east Asian markets. Since 1963, Kawasaki took complete control of Meguro, and the Meguro model K 500 cc four-stroke parallel-twin was re-badged as a Kawasaki. The Kawasaki W1 650 cc (actually 624 cc) four-stroke twin was developed from the Meguro K series, which Meguro had developed from a

BSA A7 The BSA A7 was a 500cc motorcycle model range made by Birmingham Small Arms Company (BSA) at its factory in Armoury Road, Small Heath, Birmingham. The range was launched in 1946 using a long stroke engine. An improved version based on the BSA ...

under license. Kawasaki developed the lighter Kawasaki A1 Samurai during 1966. It was quickly followed by the larger bore model, the A7 Avenger, which is similar to the Samurai. Sharing all of the Samurai components aside from

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder (engine), cylinder a ...

piston ring A piston ring is a metallic split ring that is attached to the outer diameter of a piston in an internal combustion engine or steam engine. The main functions of piston rings in engines are: # Sealing the combustion chamber so that there is mini ...

s, different mufflers with reverse cones, it also features a race-developed oiling system called Injectolube. Oil is not only injected in with the petrol as on the 250 but is also fed to the main bearings. The crankcases and crank were also redesigned for use with the Injectolube system. The A7SS Avenger has a crossover dual exhaust mounted on the left side and just below the seat. Other than the exhaust system, there are no other changes between the standard A7 and A7SS.

Engine

The engine was advanced for its time, with features normally seen on race bikes:

two-cylinder The engine configuration describes the fundamental operating principles by which internal combustion engines are categorized. Piston engines are often categorized by their cylinder layout, valves and camshafts. Wankel engines are often categoriz ...

two-stroke A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston, one up and one down, in one revolution of the crankshaft in contrast to a four-stroke engine which re ...

air-cooled Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures. Air-cooled designs are far simpler than their liquid-cooled ...

, oil injected, dual

rotary valve A rotary valve (also called rotary-motion valve) is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of ro ...

. While other manufactures had utilized the advantages of rotary disc valve induction on small single-cylinder machines, only Kawasaki and

Bridgestone is a Japanese multinational manufacturing company founded in 1931 by Shojiro Ishibashi (18891976) in the city of Kurume, Fukuoka Prefecture, Fukuoka, Japan. The name Bridgestone comes from a calque translation and transposition of (), meaning ...

produced twin-cylinder machines. Rotary disc valve induction ensures that all the fuel charge is used and not partly lost (as in a piston ported engine). As a result, it produces more power, more torque at low revs and better response throughout the rev range. The engine's initial air supply begins in an

air filter A particulate air filter is a device composed of fibrous, or porous materials which removes particulates such as smoke, dust, pollen, mold, viruses and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbo ...

canister below the seat and is drawn through a large

plenum chamber A plenum chamber is a pressurised housing containing a fluid (typically air) at positive pressure. One of its functions is to equalise pressure for more even distribution, compensating for irregular supply or demand. It is typically relatively la ...

just above the

transmission Transmission or transmit may refer to: Science and technology * Power transmission ** Electric power transmission ** Transmission (mechanical device), technology that allows controlled application of power *** Automatic transmission *** Manual tra ...

and behind the

cylinder head In a piston engine, the cylinder head sits above the cylinders, forming the roof of the combustion chamber. In sidevalve engines the head is a simple plate of metal containing the spark plugs and possibly heat dissipation fins. In more modern ...

, then down into the internal passages leading to the

carburetor A carburetor (also spelled carburettor or carburetter) is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Ventu ...

housing feeding the carburetors. The A7 Avenger has two Mikuni carburetors located on the engine's left and right sides and in line with the

crankshaft A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...

. The carburetors are enclosed and protected from the elements by carburetor covers fixed to the

crankcase A crankcase is the housing in a reciprocating engine, piston engine that surrounds the crankshaft. In most modern engines, the crankcase is integrated into the engine block. Two-stroke engines typically use a crankcase-compression design, res ...

. Inboard of each carburetor, and supporting each carburetor, is the disc cover. The rotary disc valve is housed inboard of that cover. During 1969, the

ignition system Ignition systems are used by heat engines to initiate combustion by igniting the fuel-air mixture. In a spark ignition versions of the internal combustion engine (such as petrol engines), the ignition system creates a spark to ignite the fuel-ai ...

was equipped with a

capacitor discharge ignition Capacitor discharge ignition (CDI) or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, gas turbine-powered aircraft, and some cars ...

including

thyristor A thyristor (, from a combination of Greek language ''θύρα'', meaning "door" or "valve", and ''transistor'' ) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage ...

-based switching system that increases the voltage to between 25,000 and 30,000 volts reducing the unburned fuel mixture within the cylinders. During the development of the

Kawasaki H1 Mach III The Kawasaki H1 Mach III was a two-stroke 500 cc sport bike made by Kawasaki from 1969 through to 1975. History By mid-1960s, the US had become the largest motorcycle market. American riders were demanding bikes with more horsepower and hig ...

, engineers considered using the Avenger's twin-cylinder engine bored out to create the new 500 cc two-stroke power plant as called for in the

N100 Plan The N100 Plan was the corporate code name for the top secret concept, engineering, and development of an entirely new motorcycle engine by Kawasaki Motorcycle Corporation, a division of Kawasaki Heavy Industries in 1966. Goal The goal of Kawasaki ...

Racing

A7 Avengers participate in the

American Historic Racing Motorcycle Association AHRMA (American Historic Racing Motorcycle Association) is a not-for-profit organization dedicated to preserving, restoring and competing on historic motorcycles. With over 3000 members, AHRMA is the leading vintage motorcycle racing group in Nort ...

(AHRMA) competition. Kawasaki Mach III's successfully raced with Ginger Molloy aboard his "Green Meanie" finishing 2nd just behind

Giacomo Agostini Giacomo Agostini (; born 16 June 1942) is an Italian former professional motorcycle road racer and racing team manager. He competed in the FIM Grand Prix motorcycle racing world championships from 1963 to 1977, most prominently as a member of ...

MV Agusta MV Agusta (, full name: MV AGUSTA Motor S.p.A., original name: Meccanica Verghera Agusta or MV) is an Italian high end motorcycle manufacturer. It was founded by Domenico Agusta, Count Domenico Agusta on 19 January 1945 as one of the branches of ...

during the 1970 500 cc World Championship.Motorcycle USA: Memorable Motorcycles, Kawasaki H1
/ref>

References

{{reflist, 30em Standard motorcycles A7 Avenger 350 Sport bikes Motorcycles introduced in 1967 Motorcycles powered by straight-twin engines