Kawasaki A7 Avenger
Encyclopedia
The A7 Avenger was a 350 cc Kawasaki motorcycle
. It was a standard or Universal Japanese motorcycle sold in the U.S. and abroad from 1967 through 1971.
was re-badged as a Kawasaki.
The Kawasaki W1
625 cc four-stroke twin was developed from the Meguro K series, which Meguro had developed from a BSA A7
under license. It did not sell as well as hoped because some of its competitors were faster, lighter and had better steering.
Kawasaki developed the lighter Kawasaki A1 Samurai
in 1966. It was quickly followed by the larger bore model, the A7 Avenger which is nearly a twin of the Samurai sharing all of the Samurai components aside from piston
s, piston ring
s, different mufflers with reverse cones, it also featured a race developed oiling system called "Injectolube". Oil was not only injected in with the petrol as on the 250 but oil was also fed to the main bearings. The crankcases and crank were also redesigned for use with the "Injectolube" system.
. While other manufactures had utilised the advantages of rotary disc valve induction on small single-cylinder machines, only Kawasaki and Bridgestone
produced twin-cylinder machines. Rotary disc valve induction ensures that the 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 ignition air supply began in an air filter
canister below the seat and was drawn through a large plenum chamber
just above the transmission
(gearbox) and behind the cylinder head
, then down into the internal passages leading to the carburetor
housing feeding the carburetors.
The A7 Avenger had two Mikuni
carburetors located on the engine's left and right sides and in line with the crankshaft
. The carburetors were enclosed and protected from the elements by carburetor covers fixed to the crankcase
. Inboard of each carburetor, and supporting each carburetor, was the disc cover. The rotary disc valve was housed inboard of that cover. In 1969 the ignition system
was equipped with a capacitor discharge ignition
including thyristor
-based switching system then increased the voltage to between 25,000 and 30,000 volts reducing the unburned fuel mixture within the cylinders.
This combination of displacement (338 cc), CDI system, and rotary discs produced 42 hp (30.7 KW) @ 8000 RPM gave the Avenger a power-to-weight ratio of 1 horsepower per 8.5 pounds of weight, a 0-60 mph of 5.2 seconds. At the time the A7 had the most powerful engine per cc of any road bike.
Until the 500 triple arrived the A7 was the most powerful bike up to 500 cc, add to this its low weight, only 10 lbs more than the 250, explains why the A7 was so fast.
, 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
.
Sources: Motoprofi.com
(AHRMA) comoetition.
Kawasaki Mach III's successfully raced with Ginger Molloy aboard his "Green Meanie" finishing 2nd just behind Giacomo Agostini's MV Agusta
in the 1970 500 cc World Championship. Kawasaki's
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
. It was a standard or Universal Japanese motorcycle sold in the U.S. and abroad from 1967 through 1971.
Development
Kawasaki was the last of the big four Japanese manufacturers to start making motorcycles. In 1960 it bought a share in the Meguro motorcycle company that since the 1930's had made 4-stroke singles up to 500 cc and later twins up to 650 cc for the Japanese and south-east Asian markets. From 1963 Kawasaki took complete control of Meguro, and the Meguro model K 500 cc four-stroke parallel twinStraight-two
A straight-two engine, is a two-cylinder piston engine that has its cylinders arranged side by side....
was re-badged as a Kawasaki.
The Kawasaki W1
Kawasaki W series
-Antecedents: Meguro K series:In 1960 the Akashi-based Kawasaki Aircraft Company acquired an interest in the Meguro motorcycle company, which had obtained a license to produce a copy of the 500 cc BSA A7. Meguro had been Japan's largest motorcycle manufacturer but in the late 1950s its models had...
625 cc four-stroke twin was developed from the Meguro K series, which Meguro had developed from a BSA A7
BSA A7
The BSA A7 was a British motorcycle manufactured by Birmingham Small Arms Company at their factory in Armoury Road, Small Heath, Birmingham in 1946. There were actually two versions of the A7, the original 495cc version and an improved 497cc version launched in 1950...
under license. It did not sell as well as hoped because some of its competitors were faster, lighter and had better steering.
Kawasaki developed the lighter Kawasaki A1 Samurai
Kawasaki A1 Samurai
The A1 Samurai was a production motorcycle made by Kawasaki. It was a standard or Universal Japanese motorcycle sold in the US and abroad from 1967 through 1971.-Development:...
in 1966. It was quickly followed by the larger bore model, the A7 Avenger which is nearly a twin of the Samurai sharing all of the Samurai components aside from piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
s, piston ring
Piston ring
A piston ring is a split ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine.The three main functions of piston rings in reciprocating engines are:...
s, different mufflers with reverse cones, it also featured a race developed oiling system called "Injectolube". Oil was not only injected in with the petrol as on the 250 but oil was also fed to the main bearings. The crankcases and crank were also redesigned for use with the "Injectolube" system.
A7SS
The A7SS Avenger has a crossover dual exhaust mounted on the left side and just below the seat. Other than exhaust system, there were no other changes between the standard A7 and A7SS.An unique engine
The engine was very advanced for its time, only to be seen on race bikes: 2-cylinder, two-stroke, air-cooled, oil injected, dual rotary valveRotary valve
A rotary 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 rotary valve...
. While other manufactures had utilised the advantages of rotary disc valve induction on small single-cylinder machines, only Kawasaki and Bridgestone
Bridgestone
The is a multinational rubber conglomerate founded in 1931 by in the city of Kurume, Fukuoka, Japan. The name Bridgestone comes from a calque translation and transposition of ishibashi, meaning "stone bridge" in Japanese....
produced twin-cylinder machines. Rotary disc valve induction ensures that the 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 ignition air supply began in an air filter
Air filter
A particulate air filter is a device composed of fibrous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. A chemical air filter consists of an absorbent or catalyst for the removal of airborne molecular contaminants such as volatile organic compounds...
canister below the seat and was drawn through a large plenum chamber
Plenum chamber
A plenum chamber is a pressurised housing containing a gas or fluid at positive pressure . One function of the plenum can be to equalise pressure for more even distribution, because of irregular supply or demand...
just above the transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...
(gearbox) and behind the cylinder head
Cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...
, then down into the internal passages leading to the carburetor
Carburetor
A carburetor , carburettor, or carburetter is a device that blends air and fuel for an internal combustion engine. It is sometimes shortened to carb in North America and the United Kingdom....
housing feeding the carburetors.
The A7 Avenger had two Mikuni
Mikuni
is a leading Japanese carburettor manufacturing company that was founded in 1923 and incorporated in 1948. Their business activities are centred on carburettors, fuel injectors and other automobile related equipment...
carburetors located on the engine's left and right sides and in line with the crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
. The carburetors were enclosed and protected from the elements by carburetor covers fixed to the crankcase
Crankcase
In an internal combustion engine of the reciprocating type, the crankcase is the housing for the crankshaft. The enclosure forms the largest cavity in the engine and is located below the cylinder, which in a multicylinder engine are usually integrated into one or several cylinder blocks...
. Inboard of each carburetor, and supporting each carburetor, was the disc cover. The rotary disc valve was housed inboard of that cover. In 1969 the ignition system
Ignition system
An ignition system is a system for igniting a fuel-air mixture. Ignition systems are well known in the field of internal combustion engines such as those used in petrol engines used to power the majority of motor vehicles, but they are also used in many other applications such as in oil-fired and...
was equipped with a capacitor discharge ignition
Capacitor discharge ignition
Capacitor discharge ignition or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft, and some cars...
including thyristor
Thyristor
A thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as bistable switches, conducting when their gate receives a current trigger, and continue to conduct while they are forward biased .Some sources define silicon controlled rectifiers and...
-based switching system then increased the voltage to between 25,000 and 30,000 volts reducing the unburned fuel mixture within the cylinders.
This combination of displacement (338 cc), CDI system, and rotary discs produced 42 hp (30.7 KW) @ 8000 RPM gave the Avenger a power-to-weight ratio of 1 horsepower per 8.5 pounds of weight, a 0-60 mph of 5.2 seconds. At the time the A7 had the most powerful engine per cc of any road bike.
Until the 500 triple arrived the A7 was the most powerful bike up to 500 cc, add to this its low weight, only 10 lbs more than the 250, explains why the A7 was so fast.
Almost a 500
During the development of the Kawasaki H1 Mach IIIKawasaki H1 Mach III
The Kawasaki H1 Mach III was a high-performance two-stroke 500cc production motorcycle manufactured by Kawasaki Motorcycle Corporation. It was sold in the U.S. and abroad from 1969 through 1975.-History:...
, 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
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:...
.
Appearance
- 1968: The A7 was available with either a candy red or candy blue with chrome parts and black frame. The fuel tank was colored with chromeChrome platingChrome plating, often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness.-Process:A component to be chrome plated will...
side panels which held rubber knee grips and Kawasaki flag emblem. Front fenders was stainless steelStainless steelIn metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
, rear fender was chromed, upper rear shock fork assembly, chain guard, and parts of the fork assembly were chrome plated. Upper fork, headlight and speedometer combination as well as upper rear shock and side-mounted oil reservoir covers were painted. Mufflers were seamless.
- 1969: The A7 and A7SS integrated headlight speedometer unit were separated into two independent units. The colors remained but the fuel tank was completely painted with the tank sides white and "KAWASAKI" stretching along the tank. The SS versions had cross braced handle bars and skid plate.
- 1970: Designation becomes A7A and A7ASS. The Samurai's color scheme was a pearl candy red and white. The fuel tank was red with white sides enhancing the more rectangular style shared by the Kawasaki H1 Mach IIIKawasaki H1 Mach IIIThe Kawasaki H1 Mach III was a high-performance two-stroke 500cc production motorcycle manufactured by Kawasaki Motorcycle Corporation. It was sold in the U.S. and abroad from 1969 through 1975.-History:...
. Side covers were white.
- 1971: Designation becomes A7B and A7BSS. All Kawasaki bikes had the angular fuel tanks and fading color decal replacing the white side tank coloring. This model was available in a pastelPastelPastel is an art medium in the form of a stick, consisting of pure powdered pigment and a binder. The pigments used in pastels are the same as those used to produce all colored art media, including oil paints; the binder is of a neutral hue and low saturation....
yellow or pastel white finish and fading gold/yellow decal.
Competitors
1969-1970 contemporaries and competitors of the A7 Avenger were:- Honda Dream CB350: 36 hp. 0-60 in 6 seconds.
- Suzuki T350 Rebel. 39 hp. 0-60 mph N/A.
- YamahaYamahaYamaha may refer to:* Yamaha Corporation, a Japanese company with a wide range of products and services** Yamaha Motor Company, a Japanese motorized vehicle-producing company...
(unknown)
Sources: Motoprofi.com
Racing
A7 Avengers have and can participate in the American Historic Racing Motorcycle AssociationAmerican Historic Racing Motorcycle Association
The American Historic Racing Motorcycle Association was formed in 1984 as a private business. In 1987 it was reorganized as a member owned non profit organization...
(AHRMA) comoetition.
Kawasaki Mach III's successfully raced with Ginger Molloy aboard his "Green Meanie" finishing 2nd just behind Giacomo Agostini's MV Agusta
MV Agusta
MV Agusta is a motorcycle manufacturer founded in 1945 near Milan in Cascina Costa, Italy. The company began as an offshoot of the Agusta aviation company formed by Count Giovanni Agusta in 1923. The Count died in 1927, leaving the company in the hands of his wife and sons, Domenico, Vincenzo,...
in the 1970 500 cc World Championship. Kawasaki's