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57-504: Based heavily on a licensed version of the post-war, pre-unit construction, 500cc vertical-twin BSA A7 , the bikes were clearly aimed at the market then dominated by the classic British twins of the day. Production of the original series, which saw W2 and W3 models, ended in 1974. In 1999 the W650 appeared, and was produced through 2007. In 2011 Kawasaki announced another retro version of the “W” brand,

114-462: A sequential gearbox . Most motorcycles (except scooters) change gears (of which they increasingly have five or six) by a foot-shift lever. On a typical motorcycle, either first or second gear can be directly selected from neutral, but higher gears may only be accessed in order – it is not possible to shift from second gear to fourth gear without shifting through third gear. A five-speed of this configuration would be known as "one down, four up" because of

171-555: A BSA Star Twin for an attempt on the American Class C speed record for standard catalogue motorcycles. The rules prevented major modification but Alzina was allowed to use 80 octane fuel, which together with a compression ratio of 8 to 1 enabled rider Gene Thiessen to achieve a two way record speed of 123.69 mph (199.06 km/h). In 1954 Bobby Hill won the Daytona 200 riding a rigid framed Shooting Star. (The rigid frame version

228-410: A handlebar-mounted trigger, paddle, switch, or button, and an automatically-operated clutch system. Quickshifters are electronic devices that allow for clutchless upshifts (and usually downshifts) on high-performance motorcycles with a standard manual transmission. An ECU works in conjunction with a sensor and a microcontroller ( CPU ) to cut the ignition and/or fuel injection momentarily, so

285-422: A lower speed with full versus minimal throttle. Pre-unit construction , also called separate construction, is a motorcycle engine architecture where the engine and gearbox are separate casings. In unit construction the engine and gearbox share a single housing. In many modern designs, the engine sits in front of the gearbox. From a sprocket on one side of the crankshaft, a chain or sprocket directly mounted to

342-525: A semi-auto, the rider is responsible for this choice, and they can ride around all day in top gear (or first) if they so prefer. Also, when the engine is turning fast enough to lock the clutch, it will stay fully engaged until the RPMs fall below that critical point again, even if the throttle is fully released. Below the lock-up point, partially or fully releasing the throttle can lead to the RPM falling off rapidly, thanks to

399-635: A smaller Kawasaki W175 was introduced in Indonesia for the South East Asian market thus becoming the lightest bike in the series. 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 495 cc (30.2 cu in) long stroke engine. An improved 497 cc (30.3 cu in) version based on

456-426: A three to five-speed foot-shift lever, but the clutch is automatic (usually a centrifugal clutch). This type of clutchless (no manual clutch) transmission still must have the gears shifted manually by the rider, and the system is commonly known as a semi-automatic transmission . The clutch in a manual-shift motorcycle transmission is typically an arrangement of plates stacked in alternating fashion, one geared on

513-690: Is based heavily on the post-war , pre-unit construction, 500cc vertical-twin BSA A7 design inherited from Meguro, but as time passed, the Kawasaki and BSA designs diverged. The BSA engine has a 70 mm (2.8 in) bore and 84 mm (3.3 in) stroke , whereas the W1 inherited its 72.6 mm (2.86 in) stroke from the K2 engine, adding displacement by increasing the size of its bore to 74 mm (2.9 in). This slightly oversquare (i.e., short-stroke) design favors higher engine speeds, while reducing stresses on

570-537: The Honda Super Cub ), smaller dirt bikes (such as pit bikes ), and various (mostly older) mopeds and motor scooters . Semi-automatic transmissions are often erroneously called "automatic" transmissions, which is only partially correct but not fully correct, since the rider's input is still required for switching gears, and these transmissions will not automatically change gears by themselves. Other applications of semi-automatic transmissions on motorcycles include

627-525: The Yamaha FJR1300AE sport-touring motorcycle , with the YCCS automatic clutch system, Honda 's range of 2- and 3-speed Hondamatic semi-automatic transmissions, used on various motorcycles throughout the 1970s and 1980s, and the three-wheeled BRP Can-Am Spyder Roadster motorcycle, with its SE5 and SE6 range of transmissions. Some high-performance sport bikes also use a trigger-shift system, with

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684-516: The BSA Rocket 3/Triumph Trident . The 1969 Kawasaki H1 Mach III with an inline-triple two-stroke, and the Honda CB750 's Inline-four engine into the bargain, foreshadowed the ascendancy of multi-cylinder engines. The W series engines were oil-tight and reliable, but by comparison they had low levels of performance with high levels of vibration, and were ultimately unsuccessful on the sales floor. At

741-614: The Bert Hopwood designed 650 cc twin cylinder A10. The engine in the A10 was a redesigned and improved version of the A7 engine. A 497 version of the redesigned engine was produced for the A7. Initially fitted in the new A7S Star Twin, it was also fitted to the base A7 model in 1951. The new engine had a shorter stroke with bore and stroke dimensions of 66 mm × 72.6 mm (2.60 in × 2.86 in). Most motorcycles of this period tensioned

798-594: The K1 . The K2 has a larger timing cover which distinguishes it from the model K and the BSA A7. Also the K2 chassis has a different rear subframe, fuel tank and side panels. These changes gave the K2 a typically conservative Meguro image, dissimilar to the original BSA A7. In 1965 the K2 was enlarged to 624 cc to become the Meguro X-650 prototype, which was displayed at the 1965 Tokyo Motor Show . The X-650 then became in turn

855-572: The W800 , which remained in production until 2016, then was re-introduced in 2019. A W175 was released in 2017. 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 become less competitive and it

912-429: The valves via long pushrods passing through a tunnel in the cast iron block . This system needed a considerable number of studs and nuts to fasten down the cast iron cylinder head and rockerboxes, many of them deeply recessed and requiring well-made box spanners or the then uncommon sockets. As with other British motorcycles of the period, this kind of set-up regularly led to oil leaks. In October 1949 BSA launched

969-545: The 1970s. By the late 1990s successors to the Zephyrs were based on even older generations of motorcycles with twin-cylinder engines, the V-twin engined Drifter and the vertical-twin W650 . Unlike the 1960s W series, the 1999–2007 W650 had an up-to-date engine design while holding on to the vintage British motorcycle look. The 2011–2013 W800 carries on with the W brand, and expands the range to include Café racer models. In 2017,

1026-466: The 500 cc BSA A7. Meguro had been Japan's largest motorcycle manufacturer but in the late 1950s its models had become less competitive and it was short of money. Kawasaki's investment enabled Meguro to launch its A7 copy as the Meguro K. In 1963 Meguro was taken over one hundred per cent by the new Kawasaki Motorcycle Corporation , which maintained the licensing agreement with BSA and continued to build

1083-540: The 70s, subsequent models were produced primarily for the domestic market. The penultimate model in the W series was the W1SA with stylistic changes, but most importantly with the gearshift lever on the left side and the rear brake pedal on the right side, which is the standard configuration for Japanese motorcycles. The final version was the 1973 W3 model (aka RS650 ) with upgraded suspension as well as twin disc brakes in front. W series production ceased in 1974. As soon as

1140-507: The BSA A10 engine was launched in 1950. The various A7 models continued in production with minor modifications until 1961/2 when they were superseded by the unit-construction A50 model. After the 1938 launch of the Edward Turner designed Triumph Speed Twin , BSA needed a 500cc twin to compete with it. Designed by Herbert Parker, David Munro and BSA's chief designer, Val Page , the BSA A7 was

1197-610: The K model, but due to lubrication problems Kawasaki made engine modifications and the Kawasaki K2 entered production in 1965 with improved crankshaft bearings and a larger oil pump. Since the introduction of the K2, the Meguro K model has tended to become known retrospectively as the K1. In 1965 the K2 was enlarged to 624 cc to become the Meguro X-650 prototype, which was displayed at the 1965 Tokyo Motor Show . The X-650 then became in turn

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1254-637: The W1 was released, Kawasaki realized that even an improved version of the BSA A10 (itself already discontinued) was at a disadvantage against the newer and faster unit construction British twins, the BSA Spitfire and the Triumph Bonneville T120 . The W1 also had to compete with other Japanese twin-cylinder street bikes, such as the Suzuki T500 and the Honda CB450 . If the W1 was seen as being behind

1311-451: The bike is properly in motion, so the gearbox input shaft is also rotating quickly and so allowing the engine to accelerate further by way of clutch slip - the outward pressure of the weighted friction plates is sufficient that the clutch will enter full lock-up, the same as a conventional plate-clutch with a fully released lever or pedal. After this, there is no clutch slip, and the engine is locked to and providing all of its available power to

1368-433: The clutch spring(s), allowing the engine to freewheel with respect to the transmission. Automatic and semi-automatic transmissions typically use a centrifugal clutch which operates in a different fashion. At idle, the engine is disconnected from the gearbox input shaft, allowing both it and the bike to freewheel (unlike torque converter automatics, there is no "idle creep" with a properly adjusted centrifugal clutch). As

1425-423: The clutch will drive the clutch, which can often be found behind a large circular cover on one side of the gearbox. The clutch is connected to the gearbox input shaft. For motorcycles with chain drive, the gearbox output shaft is typically connected to the sprocket which drives the final drive chain. Most modern manual motorcycle gearboxes have "constant-mesh" gears which are always mated but may rotate freely on

1482-400: The crankshaft. In addition, the new W1 had a multi-piece pressed crankshaft assembly with ball bearings and one-piece connecting rods with needle bearings, significant changes from the earlier BSA (and Meguro) engines that used plain insert type bearings and two-piece connecting rods. The BSA and Kawasaki 650cc engines were thus mechanically different, but they looked very similar. Likewise, in

1539-474: The design of its twin-loop frame, as well as its overall styling, the W1 motorcycle was clearly influenced by classic British road bikes, including shifting with the right foot and braking with the left. From 1966 to 1968 W1 engines were built with a single 31 mm Mikuni carburetor (this is only feasible in a straight-twin with a 360° crankshaft angle). Starting in 1968, the W1SS with two 28 mm Mikuni carbs took

1596-432: The feedback loop of lower engine speed meaning less friction pressure. This toggle-like mode of operation can lead to certain characteristic centrifugal-clutch-automatic behaviour, such as being able to freewheel rapidly downhill from a standstill, with engine braking only being triggered by turning the throttle briefly (and not then cancellable without braking to quite a slow, gear-dependent pace), and lockup triggering at

1653-505: The first of the BSA twin- cylinder motorcycles. The outbreak of World War II delayed the launch and several prototypes were built during the war years. The model was finally launched in September 1946 when hostilities had ended. The very first A7 off the production line was flown to Paris for the first motorcycle show after the end of the war. There was huge demand for affordable transport after

1710-407: The inside to the engine and the next geared on the outside to the transmission input shaft. Whether wet (rotating in engine oil) or dry, the plates are squeezed together by springs, causing friction build up between the plates until they rotate as a single unit, driving the transmission directly. A lever on the handlebar exploits mechanical advantage through a cable or hydraulic arrangement to release

1767-496: The largest touring motorcycles (sometimes in excess of 360 kg or 800 lbs) is sometimes such that they cannot effectively be pushed backwards by a seated rider, and they are fitted with a reverse gear as standard. In some cases, including the Honda Gold Wing and BMW K1200LT , this is not really a reverse gear, but a feature of the starter motor which when reversed, performs the same function. To avoid accidental operation,

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1824-492: The left), but today gear-changing is standardised on a foot-operated lever to the left. Traditional scooters (such as the Vespa ) still have manual gear-changing by a twist grip on the left-hand side of the handlebar, with a co-rotated clutch lever. Modern scooters were often fitted with a throttle-controlled continuously variable transmission , thus earning the term twist-and-go . Underbone and miniature motorcycles often have

1881-675: The place of the original W1. Also in 1968, the W2 (aka Commander ) emerged. The W2SS was a restyled W1SS with slightly more horsepower, and the W2TT was a high-pipe version with twin mufflers on the left side. Due to flat sales in North America the W2TT was discontinued in 1969, the W2SS ended in 1970, and finally in 1971 Kawasaki axed the W1SS. The 650 remained popular in Japan, and although some were exported to Europe in

1938-851: The placement of the gears with relation to neutral, though some motorcycle gearboxes and/or shift mechanisms can be reversed so that a "one up, four down" shifting pattern can be used. Neutral is to be found "half a click" away from first and second gears, so shifting directly between the two gears can be made in a single movement. Fully-automatic transmissions are far less common on motorcycles than manuals, and are mostly found only on motor scooters , mopeds , underbones , minibikes , and some custom cruisers and exotic sports bikes . Types include: hydraulic automatic transmission , continuously variable transmission , and dual-clutch automatic transmissions . Semi-automatic transmissions on motorcycles are also referred to as auto-clutch transmissions, or sometimes, clutchless manual transmissions. They function in

1995-414: The power being transmitted through the (still-slipping) clutch is equal to what the engine can provide. This allows relatively fast full-throttle takeoffs (with the clutch adjusted so the engine will be turning near its maximum-torque rpm) without the engine slowing or bogging down, as well as more relaxed starts and low-speed maneuvers at lower throttle settings and RPMs. Above a certain engine speed - when

2052-408: The primary chain by drawing or rotating the gearbox backwards on a hinge with threaded rods, this was known as pre-unit construction . The first A7 had a fixed gearbox, bolted to the back of the crankcase , and an internal tensioner for the duplex primary chain . However, in 1954 when the swinging arm was introduced, the re-design reverted to the older system of a separate gearbox. The electrics (as

2109-742: The prototype for the Kawasaki W1 . For the new Kawasaki big bike, the traditional look of Meguro motorcycles was replaced with a sleeker fuel tank, sportier mudguards (fenders) and other details intended to appeal to export markets, especially North America. Motorcycle transmission#Shift control A motorcycle transmission is a transmission created specifically for motorcycle applications. They may also be found in use on other light vehicles such as motor tricycles and quadbikes , go-karts , offroad buggies, auto rickshaws , mowers, and other utility vehicles, microcars , and even some superlight racing cars. Most manual transmission two-wheelers use

2166-548: The prototype for the Kawasaki W1. For the new Kawasaki big bike, the traditional look of Meguro motorcycles was replaced with a sleeker fuel tank, sportier mudguards (fenders) and other details intended to appeal to export markets, especially North America. The Society of Automotive Engineers of Japan (in Japanese) , includes the 1966 Kawasaki 650-W1 as one of their 240 Landmarks of Japanese Automotive Technology . The Kawasaki W1

2223-558: The reliability of the design. All three bikes were randomly selected from the production line, picked up Gold medals and earned BSA the Team award as well as the Trophy. The three bikes were ridden by Brian Martin, Fred Rist and Norman Vanhouse. From Birmingham the team rode to Vienna then on through Germany, Denmark, Sweden and Norway before returning safely and with a clean sheet to Birmingham . Also in 1952 American BSA dealer Hap Alzina prepared

2280-408: The reverse is often engaged using an entirely separate control switch - e.g., a pull-toggle at the head of the fuel tank - when the main gearshift is in neutral. In earlier times (pre-WWII), hand-operated gear changes were common, with a lever provided to the side of the fuel tank (above the rider's leg). British and many other motorcycles after World War II used a lever on the right (with the brake on

2337-504: The rider can switch gears. Bi-directional quickshifters are technically considered semi-automatic since clutch actuation isn't required whatsoever, however, mono-directional quickshifters, such as those used on the 2016 Kawasaki Ninja ZX-10R and the Ninja H2/R , only work on upshifts, and the rider still has to manually actuate the clutch and blip the throttle on downshifts, so it's not really semi-automatic, in that sense. The weight of

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2394-448: The same time that production of the W series was ending in Japan, Kawasaki came up with a formula for successful four-stroke street bikes in its Z series . Kawasaki retro style motorcycles began with the Zephyr range, available in Japan as a 400 cc model. These retro-bikes evoked nostalgia for classic motorcycles from decades earlier, inspired by the Z series inline-fours from

2451-471: The same way as a conventional fully-manual motorcycle with a sequential gearbox , except they utilize a fully-automatic clutch system, or sometimes torque converter , but still require the rider's input to manually actuate change gears. They are much less common than motorcycles with conventional manual transmissions, typically use a centrifugal clutch , and are mostly found on smaller motorcycles, such as minibikes , underbone (step-thru) motorcycles (e.g.,

2508-428: The throttle is opened and engine speed rises, counterweights attached to movable inner friction surfaces (connected to the engine shaft) within the clutch assembly are thrown gradually further outwards, until they start to make contact with the inside of the outer housing (connected to the gearbox shaft) and transmit an increasing amount of engine power. The effective "bite point" is found automatically by equilibrium where

2565-579: The times, then Kawasaki came back with a two-stroke engine that was clearly ahead of its time, in the 1967 Kawasaki A7 Avenger with performance at least equal to the W1. The following year the W series (as well as the British bikes) faced a new competitor in a state-of-the-art twin from Yamaha, the XS650 . In 1968 the domination of the inline-twin engine for high-performance street bikes came to an end when Triumph Engineering developed an inline-triple engine for

2622-426: The transmission; engine rpm is now dependent on the road speed and the current gear ratio (under either user control in a semi-auto, or reliant on-road speed (and sometimes load/throttle position) in a CVT setup). In a typical CVT, the gear ratio will be chosen so the engine can reach and maintain its maximum-power speed as soon as possible (or at least, when at full throttle, in a partially load-dependent system), but in

2679-413: The war and the simplicity of the A7 twin was helped along by the slogan 'It's time YOU had a BSA!'. The 495 cc (30.2 cu in) twin cylinder engine produced 26 bhp (19 kW) and was capable of 85 mph (137 km/h). The engine had a long stroke with a bore and stroke of 62 mm × 82 mm (2.4 in × 3.2 in). A single camshaft behind the cylinders operated

2736-430: Was a hinged rear mudguard that lifted up to allow the rear wheel to be removed more easily. Plunger rear suspension was offered as an option to the rigid frame from 1949. Concerned about the high wear rate of the plunger suspension that lead to poor handling, a swinging arm frame was introduced in 1954 and the rigid and plunger frames discontinued. All models are swinging arm frame unless otherwise indicated. The A7

2793-402: Was a special order from the factory). The race had one straight asphalt and the other on the beach during the 1950s. Of the 107 starters only 44 finished. Shooting Stars finished 1st, 2nd, 4th and 5th. A BSA Gold Star finished in 3rd. 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

2850-479: Was introduced in 1954 with a new swinging arm frame. The engine had a hotter cam, and compression was upgraded from 6.6:1 to 7:1. Power was up to 30 bhp (22 kW) at 5800 rpm, with a top speed of just under 90 mph (140 km/h). The earlier models had a dark green frame and a separate carburetor manifold fitted to the alloy cylinder head. By the end of production in 1962 the BSA Shooting Star

2907-467: Was launched in 1947 with a rigid frame and the "long stroke" engine with iron barrels and cylinder head. Plunger suspension was offered as an alternative from 1949. The engine was changed to the shorter stroke A10 based design in 1951. The rigid frame was discontinued in 1953 and the plunger in 1954. From 1954 the swinging arm frame was produced, and the name "Flash" given to the model in the US market. An alternator

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2964-524: Was offer as an alternative to the dynamo from 1961. Production ceased in 1962 when the unit construction A50 was introduced. In response to competition from the Triumph Tiger 100 , BSA launched the A7SS Star Twin. The new model had increased compression ratio . It had the later A10 based engine and the latest design of cylinder head with austenitic steel inlet and exhaust valves. The inlet manifold

3021-403: Was separate from the cylinder head so twin carburettors could optionally be fitted. The uprated engine was fitted to a plunger frame and finished extra chrome. The model was produced with an option of rigid or plunger frames. In 1953 a new alloy head was fitted together with an Amal Monoblock carburettor. The model was discontinued in 1954 in favour of the "Shooting Star" model. The Shooting Star

3078-456: Was short of money. Kawasaki's investment enabled Meguro to launch its A7 copy as the Meguro K . The BSA A7, Meguro K and their respective derivatives have an overhead valve (i.e., pushrod) straight-twin engine with a pre-unit construction architecture. All have a 360° crankshaft angle , which provides an even firing interval between the two cylinders but high vibration caused by the two pistons rising and falling together. In 1963 Meguro

3135-491: Was taken over one hundred percent by the new Kawasaki Motorcycle Corporation , which maintained the licensing agreement with BSA and continued to build the K model, but due to lubrication problems Kawasaki made engine modifications and the Kawasaki K2 entered production in 1965 with improved crankshaft bearings and a larger oil pump. Since the introduction of the K2, the Meguro K model has tended to become known retrospectively as

3192-594: Was the culmination of the development of the BSA A7, with a black frame with light green tank, mudguards and side panels, it had an alloy cylinder head, a duplex cradle frame with swinging arm rear suspension, full-width cast iron hubs and 8-inch drum brake at the front with a 7-inch at the rear. In 1952 three BSA A7s were entered for the Maudes Trophy and the International Six Days Trial , achieving 4,500 miles (7,200 km) without problems and confirming

3249-431: Was universal for larger British motorcycles of the period) consisted of two independent systems, the very reliable and self-contained Lucas magneto , with a dynamo generator to charge the battery and provide lights. Carburation was initially a single Amal remote float Type 6. Later Amal TT and then 376 Monobloc carbs were used. The A7 was launched with a rigid frame and telescopic front forks. One useful feature

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