Chang Jiang simplified Chinese 长江; pinyin: Cháng Jiāng) is the transcribed brand name of Motorcycles that were once manufactured by the China Nanchang Aircraft Manufacturing Company. It takes its name from the Chang Jiang River, also known as the Yangtze or, in English, the Long River.
The company's CJ750 motorcycle is based on the 1956 Soviet IMZ (Irbitski Mototsikletniy Zavod) M-72, which in turn was derived from the 1938 BMW R 71.
They were originally produced for the Chinese military and are powered by an air-cooled, four- stroke, flat-twin engine displacing 746 cc. The rear wheel is shaft-driven.
The Chang Jiang 750 is unique in all the world for having the longest production run of any vehicle, more than 70 years. From 1938 until today it has been in nearly constant production. First produced as the BMW R71 (1938-1941), then in Russia as the M72 (1942-1963), and lastly in China (1957-today) as the Chang Jiang 750 (as the models M1, M1M, and M1S). While the design has evolved slightly, especially as each country began their production run, it remains firmly 1930's/1940's technology, with some parts still interchangeable with an original R71.
The history of the Chang Jiang 750 is at its core the tale of the migration of its design (and perhaps tooling) from Germany, to the Soviet Union, and ultimately to China. Official records have been lost to war or kept state secrets so all we have are competing theories backed up by plausibility and scant proof.
There are three leading theories which use as the mechanism of R71 technology transfer: reverse engineering, espionage, and official licensing.
From Germany to Russia in the 1940's
War was on the horizon, and the Russians knew it. They began modernizing their military and needed a replacement for their aging PMZ A-750. The BMW R71 would likely have seemed a reasonably modern, reasonably economical, and reasonably available replacement.
The 750cc engine of the R71 was a flathead, opposed twin which boasted a square bore and stroke design that provided 22 HP. The conventional pressed steel frames of earlier bikes were abandoned in favor of the higher strength oval tube frame, which was better able to cope with the additional stresses of a sidecar attachment.
The United States believed the bike was so advanced and reliable that they contracted with Harley-Davidson to build 1,000 copies (1942/1943 Harley model XA). It was no surprise that Russia wanted to mass produce the bike and press it into service. How it was made available to them is debatable.
Theory #1: Soviets reverse engineer BMWs they buy through Sweden
One theory has it that in 1940 the Soviets bought as many as five BMW R71s from neutral Sweden. These bikes were shipped to Russia where they were tested/evaluated and ultimately reverse engineered. Many (if not all) of the bikes were disassembled. Engineering blue prints/drawings and casting molds were made of all parts. Within two years the Soviets were producing the very nearly indistinguishable M-72.
Theory #2: Soviet spy steals blueprints and bikes from BMW
Another theory has it that in 1940 a Soviet aircraft engineer named Serdjukow, an employee at BMW's Munich manufacturing plant from 1935 to 1940, was able to get a hold of R71 blue prints and send them (along with several bikes) to mother Russia. Within two years the Soviets were producing the very nearly indistinguishable M-72.
Theory #3: BMW sells the R71 and its toolking to the Soviets
And finally, in this theory, BMW licenses the technology and sells the original BMW tooling to the Soviets in 1940 or early 1941, after production of the R71 is dropped in favor of the more aggressive and militarized R75 ("Elephant").
Though the R71 was an important and evolutionary bike, the march towards war convinced the German war ministry to abandon cost limitations and develop the R75, a sidecar bike whose capabilities far exceeded those required by the roles imagined for the earlier R71. In early 1941 R71 production wrapped up, having produced 3,458 units since 1938.
As early as the 1930s, a Russian company, Uralmoto Zavod, was producing motorcycles and sidecars in co-operation with the German company BMW. There was something in it for both sides, Russia had already recognized that German technology was far superior to theirs, and Germany needed greater production resources.
Under the Molotov-Ribbentrop pact Germany supposedly shared the designs and tooling for their now abandoned BMW R71 with the Russians.
However it happened, it happened. In February 1942 the M-72 went into production, and on 25 October 1942 the first M-72s were sent into battle. Over the course of the war, 9,799 M-72 motorcycles were produced.
The USSR's advances, largely based on their capture of the BMW R75 technology and tooling at the end of WWII gradually led them to the conclusion that the side-valve bikes were obsolete. As they began dropping their R71-based motorcycles in favor of the R75-based ones they began selling some of the R71-based sidevalves (M72) to China in the mid-1950s. Soon after the Russians and Chinese agreed to a deal by which China got the tooling the Russians were abandoning, so that the Chinese could produce their own R71 (M72) derived bikes. China wasted no time in dropping the KS 500 based machine for the tried and tested BMW R71/M72 design motorcycle.
This new Chinese bike, based on the R71/M72 and now named the Chang Jiang 750, entered production on 30 November 1957 at state-owned Gan Jiang Machinery Factory (guo ying gan jiang ji xie chang). The early production was using a lot of Russian M72 parts such as fenders, frames, wheels, ignition keys, switches ,etc. Even some complete Russian-made M72s were relabeled as the Chang Jiang 750. Others had the Russian engine replaced with a Chinese made one. These early Chang Jiang 750s are so similar to the M72s that telling the difference can be difficult, though not impossible. Among the differences, Russian engine casings are smoother than Chinese ones. There are also differences in the bike’s frames, sidecar’s frames, and in the front fenders. More specifically, the fender on the Chinese bikes are two-piece attached together with bolts and screws where the Russian made are one piece attached by rivets.
|Chang Jiang 750 M1 Type I|
The drivetrain on the Chang Jiang has been revised several times since production began. From 1957 until 1966 Chang Jiangs were fitted with a Type I engine and transmission. This drivetrain was almost identical to the German R71 and the Russian M72.
Chang Jiang 750 (M1: Type II)
In September 1966 Chang Jiang began production of the Type II engine and gear box, but it was not until 1972 when the Type II engine replaced the Type I in general use. This continued use of the Type I engine in new 1966-1972 bikes was a result of a large surplus of Type I parts and engines. With so many Type I engines in use, parts for it were still in production until the early seventies. As time went on the military would service any Type I bikes and replace engines and/or gearboxes with Type II versions for ease of maintenance, parts availability, and improved engine characteristics. Many bikes with Type I engines had their original gear box replaced with Type II gear boxes. The most noticeable visible difference between the Type I and Type II engine is the location of its dipstick; the Type I engine has the dipstick at the bottom of the engine. All engines manufactured with a serial number of 661802 and higher are Type II.
|Chang Jiang 750 M1 Type II|
At some point in the 1960s, the factory name changed to state-owned Chang Jiang Machinery Factory (Chinese name guo ying chang jiang ji xie chang), formerly guo ying gan jiang ji xie chang.
In 1969, the Chang Jiang 750 underwent some minor design changes, primarily related to the sidecar frames and headlight-mounted switches. Gas tanks with tool boxes built-in (similar to those of the R71 and R75) also began to enter production around this time.
Birth of the M1M and M1S
At the end of the 1970s the factory was once again merged into the airplane manufacturer GUO YING HONG DU JI XIE CHANG (Anyone know the English name?). Also in the late 1970s the Chinese started production of a 6v over head valve (OHV) 30 horse power engine. Only a few of these original engines are to be found today, being quickly replaced in 1980 by a 12v OHV, 30 horse power engine.
In December 1980, a small quantity of an engine called the Chang Jiang 900 was produced. This 900 cc OHV engine was an answer to the acquisition by the armed police of BMW motorcycles. Only a few of these bikes/engines were produced (probably no more than 10). Of those produced, only three engines have been found.
|Chang Jiang 900|
In the mid-1980s the Chinese realized the original R71 side valve engine were somewhat less than state-of-the-art and began to work on upgrading their engine design. The result was OHV engine technology, of Russian origin. It is not known whether or not this technology was purchased from Russia or perhaps was the result of Chinese reverse engineering. Whatever the case it did not take long before a OHV 750cc-boxer engine, remarkably similar in design to the BMW /2 engine, entered production at the Ministry of Aviation and Space Nan Fang Engine Factory in Zhu Zhou Hu Nan province (Chinese name hang kong hang tian gong ye bu nan fang dong li ji xie gong si).
|Chang Jiang 750 M1S|
In 1986, having seen benefits in the 12v electrics and some of the other improvements brought out with the OHV, the Chinese revised their sidevalve/flathead models and now produced sidevalve/flatheads with 12 volts and a gear box with reverse.
The official production off the Chang Jiang stoped around the Millenium.