The history of the W1 can be traced back to 1960 and the early K1, a motorcycle developed by the Japanese motorcycle manufacturer Meguro. Meguro had first started producing motorcycles back in 1909 and had modeled the K1 on the English BSA A7 as a replacement for their single cylinder Meguro Z7.
It was early days, and most Japanese motorcycle manufacturers at the time were basically building bikes copied from American and European models, and particularly in the large displacement categories.
For its day, the K1 was an advanced design and showcased modern-day manufacturing techniques with its Air-Cooled , 4-stroke, Twin OHV 496cc engine mounted in a double-cradle frame.
In 1960, Meguro Works entered into a business relationship with Kawasaki Aircraft Company Ltd., leading to a full merger in 1963. Therefore, although the K1 was developed and produced by Meguro, selling it was left to Kawasaki Motor Sales Co., the forerunner of Kawasaki Motorcycle Co.,Ltd. At the time, the Kawasaki engineers were so deeply engaged in the development of a 4-stroke engine for small cars that they had no time to develop anew motorcycle engine. But by the end of 1962 the four-wheel project had ended and some of these car engineers transferred to Meguro and took over the project. There were two projects that the developers had to tackle: the SG (a single-cylinder 250cc OHV) and the K1.
However, the engineers still wanted to overcome some basic design flaws in the K1 engine. Because the sales side wanted to maintain the impressive appearance and dignified look of the K1, it was decided to remodel the engine only, and in 1965 they remodelled the engine only, and in 1965 the remodeled K1 was introduced as the K2. (The changes included increased oil pump capacity, improved crankshaft bearings, etc. The Y-shape cover, the distinctive feature of the W models, was adopted at this stage.)
However, both the K1 and K2 still shared the basic weak points of the BSA A7. The K2 was exported to the US for a test in response to the expanding American market for 4-stroke motorcycles. Unfortunately, it was rejected for a lack of power.
The answer was the W1 which was developed as a large, high-performance, 4-stroke based on the K2. With this new model, the basic problems found in the lubrication system (already improved in the K2)and the weakness in the crank's big end durability was solved by going to a built-up crank. But their was insufficient time to implement the intended changes in the valve train (making it an O.H.C.). As far as the frame was concerned, the conventional tubular frame from the BSA A7 was used unchanged.
The frame building technology that Kawasaki inherited from Meguro was the quite advanced for its time, and most of the models following the K1 adopted tube frames because they were comparatively easy to make. Even though Kawasaki had developed a 4 stroke engine much earlier, the K1,K2 and W1 were typical 4-stroke motorcycle models for their day and were, so to speak, textbook models reflecting the then-current design and production technologies.
The W series entry into the US market was rather unsuccessful because it was too similar to the K models in basic structure and lacked a feeling or impression of being "new". The W models also mimicked too much the look of the BSA A7 for an American tastes, even though internally the engine was much improved from the BSA.
The W1 engine featured the larger bore of the K models and included a separate primary drive and transmission. The frame welding techniques came directly from the K models. Prior to the W1 Kawasaki only sold 2-strokes on the US market, but with the debut of the W1 it joined Honda in becoming one of the first Japanese motorcycle manufacturers to produce 4-strokes.
While Honda had produced only 4-strokes from the beginning, Kawasaki's entry into the US the market was based on predictions of increased sales for large displacement 4-strokes in the near future.
The 624cc engine of the W1 was one of the first large-displacement Japanese motorcycles. However, the way motorcycles were used in America was quite different than expected and the W1 was found "unsuitable" for the American market. On the other hand, in Japan it was well received and became famous for its unique OHV vertical twin sound and individual style.
KZ650 / Z650 History
The Kawasaki KZ650 as it was known in the USA, or Z650 as it was know every where else, was truly the 'Son of Z1' as both the Z1/900 and the Z650 were designed by Gyoichi “Ben” Inamura in the mid seventy's. The Z650 came from the idea for a bike that was not too heavy and not too big, but with the character of a sport bike.
Important in the design of this bike was that it had to the agility of a 500 with the performance of a 750 and have the capability to drive long distances without the rider getting too tired. It was indeed the best all round bike that Kawasaki had released so far. The premiere release took place in the UK in 1976 where the world press had the opportunity to see and test the machine for the first time. It was announced as a bike with the impressive performance of the 500 and 750 CC three cylinder two-stroke engines combined with the suppleness of the Z900. As well as the 4 in 2 exhaust system, the huge cylinder head made you think that you have a Z750 rather than a Z650. The 64bhp was claimed with a dry weight of only 465lbs, making a top speed of nearly 120 mph possible. But more importantly, this new model handled like no other Kawasaki. For once all the available power could be used in relative safety.
During its lifetime the Z650 gained a reputation as a good and reliable around bike. It was build until 1983, and was followed by the liquid cooled GPZ600 of Kawasaki. The Z650 engine block itself looks like a smaller version of the block of a Z900, but it was a complete new design. Lot's of things were re-designed to make the engine run smoother and make less mechanical noise.
Plain bearings replaced the Z1 roller bearing supporting the crankshaft but more significantly a Hi-Vo chain was the main drive between the crankshaft and the transmission versus the direct gear drive of the Z1. These enhancements reduced manufacturing costs but also made it a quite comfortable bike too, even when driving long distances. A bike to have lots of fun with!! Even after more than twenty years!!
STARTING FRAME NUMBER: KZ650B-000001 This four-stroke four-cylinder motorcycle boasted double overhead camshafts just like the bigger Z1 and Kawasaki claimed 64 BHP from the 652cc motor. Unlike the Z1, the 650 used a plain bearing crankshaft and used a primary drive chain instead of a gear driven unit. A single 245mm disk was used up front with a 250mm drum on the rear, more than enough to handle this relatively lightweight bike. It was offered in two colours, candy super red or candy emerald green. 2 of 3 9/11/2005 4:37 PM 1978 Z650-B2
STARTING FRAME NUMBER: KZ650B-027501 Very few differences were made to the B2. The front brake calliper was reversed to the back of the fork leg and the front master cylinder was changed from a round item to a triangular one. The charging system was changed from a three-phase system to a two phase and the regulator and rectifier was now a combined unit. The cam chain tensioner was changed to an automatic unit and a hazard switch was added to the left-hand switchgear. Needle roller bearings were now used in the swing arm instead of the previous model bushes and slight modifications were made to the carburettors to improve low speed operation. The fuel tap was replaced with a diaphragm type unit. There were also slight detail changes to the outer engine cases to incorporate the new lower case Kawasaki logo. The front footrests were now rubber mounted to combat vibration and the front forks were slightly modified. 1978 Z650-C2
STARTING FRAME NUMBER: KZ650C-010001 This was better known as the Z650 CUSTOM. The motor was a standard B2 unit but the custom was much modified elsewhere. Kawasaki fitted seven spoke alloy wheels with twin disks up front and a disk at the rear. The bold new graphics made this model stand out from the crowd and the C was a very good seller. There was a C1 model in the USA in 1977. 1979 Z650-B3
STARTING FRAME NUMBER: KZ650B-046201 The only difference over the B2 model was a change of graphics and a return to the original green and red colours. Sales once again picked up. The new lower case tank badges were also used. This time the red colour was described as candy persimmon red. 1979 Z650-C3
STARTING FRAME NUMBER: KZ650C-022801 The C3 used the new all weather sintered disk pads and braking in the wet was much improved. The bike was once again only offered in one colour, luminous dark blue. The rear calliper was changed to accept the new square sintered pads. The side panel badges were also slightly changed. This was also a C4. 1979 Z650-D2 (SR)
STARTING FRAME NUMBER: KZ650D-010601 It was basically a C3 with slightly 'chopper' styling. Chrome plating was used on the headlamp shell, clock lowers and chain guard. The rear tailpiece was dropped in place of a painted rear fender. The front exhaust downpipes were crossed over and the mufflers were made a bit shorter. The rear wheel was now a small but fat 16-inch item for that all-important custom look. There was also a D1 in 1978 and an E model, which were very similar but did not have as much equipment, having only one disc at the front and a drum rear brake. 1980 Z650-D3
STARTING FRAME NUMBER: KZ650D-026001 The only difference over the D2 was a change in colour and graphics. 1980 Z650-F1
STARTING FRAME NUMBER: KZ650F-000001 The F1 was basically a cross between a C and a B model. It had the alloy wheels but kept the drum brake at the rear instead of a disk. It was offered in three colours, blue, red or green. 3 of 3 9/11/2005 4:37 PM 1981 Z650-F2
STARTING FRAME NUMBER: KZ650F-007201 The F2 was much modified over the F1 model. It incorporated many of the larger Z750E parts. The motor was now finished in black and used transistorised ignition instead of points. The front end from the 750E was grafted on meaning a change to the brakes, front wheel and clocks. The kick-starter pedal and shaft was removed from the engine just like the Z750E. A passenger grab rail was also fitted. 1981 Z650-D4
STARTING FRAME NUMBER: KZ650D-028101 Basically a SR version of the F2 model. 1982 Z650-F3
STARTING FRAME NUMBER: KZ650F-012401 There was one major change for 1982, CV carburettors were fitted. The larger 32mm carburettors also needed the air box assembly from the Z750E/L models. 1983 Z650-F4
STARTING FRAME NUMBER: KZ650F-014301 This was the last of the 650 models, Kawasaki was now concentrating on the GPz range and there was no place for this previous best seller. The outer engine cases were similar to the Z750L model. There was also a Z650H model, which was a 'CSR' model with chopper styling.
h4>There are forums and clubs and blogs and aftermarket parts manufacturers dedicated to the Zephyr, which kinda surprised me because I always thought Kawasaki didn't go far enough in making this model line stand out more. It hit the streets looking like a rather out-dated naked bike compared to it's contemporaries. So it's great to see that owners have taken it upon themselves to create bikes that look just like the Z/KZ superbikes of the '70s.
The Kawasaki Zephyr is a range of retro-styled naked superbikes, manufactured during the 1990s. All models were built by Kawasaki with air-cooled, transverse inline, dual-overhead-cam, four-cylinder engines. There were a number of Zephyr models available, in four engine capacities - 400, 550, 750, and 1100cc.
The 400 was produced for Japan since 1989 due to the demand for 400cc motorcycles in that market. It was very popular. Many aftermarket parts were produced, with companies like Over Racing producing exhausts, swingarms, fairings and engine modifications. Zephyr styling is roughly based on the old Kawasaki Z1, with twin shock rear suspension, a relatively upright riding position and air-cooled power units. The 400, 550 and 750 engines were developed from the old Z400/500/550/650/750/900 series. The 1100 engine is based upon the venerable air-cooled DOHC, eight-valve inline-four that traces its roots back through the GPz1100 to the Z1000. It is the only Zephyr built with two spark plugs per cylinder. The Zephyr offered the customer retro styling coupled with simplicity and reliability. Performance of the line was adequate for normal riding and the engines were tuned for low to mid range power.
The Zephyr started the Naked/Retro bike boom in the UK and Europe in the early 1990s and for a while moved Kawasaki to the 2nd best selling manufacturer of motorcycles in the UK Market
The Zephyr Z750 engine reappeared in the late 1990s in the short lived ZR7.
The Zephyr 1100 had a Z1 restyle in its last year of sale including a return to wire wheels. Wire wheels also appeared on the 750. It was replaced in the Kawasaki UK range by the popular Z1100R styled ZRX1100 (later ZRX1200).
The ZRX series of motorcycles had a great impact on the growing market for retro style motorcycles, particularly in the United States. It was modeled after Kawasaki's superbike championship winning KZ1000R-S1 that propelled Eddie Lawson to Superbike dominance in the early 1980s and even spawned an international owners association known as the ZRXOA (ZRX Owners Association).
It would be fantastic if there were more homages to the Big Fours' classics. But the Zephyr started it all and here's hoping there's plenty more to come!
Just check out Google Images for dozens more superbly modified Zephyrs.