What is a Chang Jiang? Changjiang (Great River) is a Chinese motorcycle brand. The engines were built in different factories, including Dong Tian Enterprise Co. Ltd. Hangzhou but largely in Nanchang. Chang Jiang (also spelled Xiangjiang) is a copie of the first model of Ural. That was another copy from a BMW R71. (read the whole story here on the site) They used 750 cc sidevalve engines, mainly in three-wheeled transport vehicles and the flagship Black Star, are thus derived from the first Ural M72. Under the name Black Star and Cossack, the Chang Jiang motorcycles sold in western countries, especially in England. The Chinese get the models from Russia when the Russians switched to overhead valve technology. See more about the History.

The 750cc heavy Chang Jiang were built in Shanghai Motorcycles Factory, Lanying engine plant in Hunan, the Suzhou Changjiang Machine and probably the Hongdu Machinery Factory. Among the names Tai Shan, Tian Dong and Yangtze, the models are also built in the Tai Shan Production and Construction Motorcycles Factory and the North China No.2 Factory. Further 750 cc BMW-like engines delivered under the name Chang Dong. There is also a 900 cc model.

Reconstructed (refurbised) models are still being sold by Dong Titan and a number of smaller producers. (see linkpage) Dong provides also other machines, such as replicas of the (old) Jawa 535 and the famous Solex moped. Furthermore, the Crown Prince 50 -, 70 - and 90 cc cylinder with customs, minibikes and ATVs.

(Text from Wikipedia but reworked)
Depending on the model, the CJ750 motorcycle is equipped with either a twin-cylinder side valve "Flathead" engine, or an Over Head Valve (OHV), four-stroke, air-cooled engine. Both of these engines use the original boxer engine design principle. The horizontally apposed cylinder arrangement ensures proper cooling and easy serviceability. During hot weather operation it is important to observe the engine, power train and the running gear to ensure that overheating does not occur. Under normal operating conditions overheating will not occur after the motorcycle has been run-in, unless however, the machine is fully loaded and operating under high engine RPM for extended periods. As a guideline, the temperature of the cylinder heads should not exceed 180C-220C. The crank gear incorporates the cylinders, the pistons with piston rings and pins, the connecting rods with bearings and the crankshaft with the flywheel. The engine cylinders are identical in design and interchangeable. A gasket and o-ring are fitted between the cylinder and the crankcase. When mounting the left-hand cylinder, see that the holes in the gasket are in line with the oil feed and drain back holes crankcase.
Piston, piston rings and piston pins
Engine pistons have four milled groves (side valve) or three milled grooves (ORV) for the piston rings. The piston is connected to the connecting rod by means of a floating gudgeon pin, which is retained by circlips. When installing new piston rings the ring gap clearance must be checked and if necessary adjusted to 0,3 mm to 0,4 mm. Piston to bore clearance should be set to 0,07 mm.
Crankshaft and connecting rod.
The engine crankshaft and connecting rod assembly are of a multi piece design with the crankshaft and (conrod big end) running on roller bearings. The piston gudgeon pin runs on a brass bush in the conrod small end. Servicing of the crank is not recommended unless the correct equipment to verify crank accuracy is available. It is generally cheaper to replace the crankshaft and connecting rods as a unit in the cases of severe damage.
The crankcase accommodates the cylinders, the timing gear and auxiliary mechanisms, as whil as serving as the oil reservoir with the oil pan. The engine is provided with forced ventilation of the crankcase. The breather is located in the timing gear cover. The crankcase ventilation system is routed to the air cleaner.
Valve Timing Gear.
The valve timing gear controls the intake of the fuel/air mixture into the cylinders and waste gas exhausted into the atmosphere. The intake and the exhaust valves are interchangeable on side valve engines, but not on ORV engines. The camshaft rotates in two bearings inside the engine crankcase, a ball bearing at the front and a bronze blind bushing at the rear. Correct valve timing is obtained by aligning the mark grooves on the timing gears. This must be carefully observed during disassembly and reassembly of the engine
Valve adjustment
It is very important to adjust the valves properly. Valves are adjusted with a cold engine. The clearance should be 0,1 mm cold or 0.07mm hot. In service, the clearances will change due to bedding-in of valve train components. It is important to readjust the clearances after grinding or partial disassembly of the valve mechanism. For this purpose, put a pan under the cylinder head, take off the head cap and drain off accumulated oil. Turn the crankshaft using the kick lever. When the intake valve begins to close, set the clearance for the exhaust valve, and when the exhaust valve begins to open, set the intake valve clearances. Check the clearance between the larger end of the rocker arm and the valve stem. If the clearance happens to be larger or smaller than specification, slacken off the locknut and by turning the adjusting bolt in or out, set the required clearance with a feeler gauge. Lock the adjusting bolt with the locknut and then check the clearance again. In the course of running in, check valve clearances after 500 km and again at 3000 Km . Readjust clearances on the cold engine only.
Engine maintenance
During everyday preventive maintenance, clean the engine from mud and dust paying special attention to the cooling fins, fouling of the cooling fins will reduce the engine cooling. Check engine crankcase, cylinders and cylinder heads for leaks of oil and fuel.
Oil Filtration
The CJ7S0 is not fitted with the modem disposable oil cartridge type filter but utilizes a oil slinger type centrifugal filter which is integrated with the crankshaft. The oil slingers will only require servicing at approximately 70000 km. The servicing of the slingers requires the removal and disassembly of the crankshaft. This is a specialist procedure and should preferably be carried out by a motorcycle dealer with the necessary expertise.
Oil Consumption

If oil consumption exceeds 500 ml per 500 km, replace the piston rings. Note: Facts about oil consumption.

Petrol engines depend upon oil to lubricate cylinder walls, pistons and piston rings. With each stroke of the piston a thin film of oil is left on the cylinder walls and on the combustion stroke it is burned away by the combustion flame. If an engine burns just one drop of oil on every firing stroke, it would use approximately 200ml oil per kilometer. Consumption of this amount is unheard of in the internal combustion engine but all engines do however use some oil to prevent rapid engine wear. The rate of oil consumption depends upon the quality and viscosity of the oil in the crankcase, the engine r/min, the temperature and the amount of dilution and oxidization in the crankcase. High speed operating conditions will greatly accelerate oil consumption due to the inability of the piston rings to scavenge the oil completely at higher r/min and high engine temperatures. It has been proved in tests that an internal combustion engine uses seven times the quantity of oil at 100 km/h than it does at 60 km/ho Modern engine manufacturers consider oil consumption of up to 2,0 liters per 1000 km during the first 10 000 km to be considered normal, as it can take up to 10000 km for the piston rings to bed in to the cylinder walls. Consumption should then drop to approximately 1 liter per 1000 km. Bearing in mind that the design of the CJ 750 has its origins in the pre-war era, similar oil consumption to this is could be considered to be normal for a C1750. It must also be borne in mind however that the total crankcase capacity of the CJ 750 is a little less than 2 liters and it is therefore imperative that the oil levels be checked on a regular basis. Recommended that a daily check on the oil level be performed, and that the oil level be checked during every fuel stop on a long distance trip.

Power train
The power transmission of the motorcycle is comprised of the clutch, gearbox, propeller shaft and the final drive
The clutch transmits torque from the engine to the gearbox, and allows disengagement of the engine from the gearbox during shifting of the gears, and when braking to a stop. The clutch allows smooth starting of the motorcycle from rest, as well as protecting the power train against damage when the engine speed or drive wheel speed is suddenly changed. The clutch is of dry double-disk design. The clutch release mechanism is controlled by means of the lever on the left grip of the handle bar. With the clutch lever released, the engine is engaged to the gearbox. When the clutch lever is squeezed, the engine is disengaged from the gearbox. Use the clutch lever for starting from rest and for gear shifting. Under heavy traffic conditions avoid slipping the clutch excessively, as this will cause heavy wear of the disks. When stopped for any length of time (e.g., a traffic light), it is best to shift into neutral and release the clutch lever. Holding the clutch in for long periods will cause excessive heating and wear.
Clutch adjustment.
The clutch control lever (located on the handle bar) should have a 5 - 8 mm play. This play is measured at the lever end. The normal play of the lever ensures full engagement and disengagement of the clutch. If the play is smaller than specified, the clutch slips. With excessive play, the clutch drags, i.e. the disengagement is incomplete. Use the adjusting screw on the clutch control cable to adjust the play.
Gearbox with Reverse Gear.
The principal parts of the gearbox are the split box with covers, clutch shaft and main shaft with gears and shift sleeves, the gear shift mechanism, the kick starter and the reverse gear engagement mechanism. Shafts. The clutch shaft is installed in the ball and roller bearings. The shaft is made integral with the gear rims of the 1st, 2nd and 3rd gears. The gear of the 4th gear is fixed on a segment key. The main shaft is set on two ball bearings. The pinions of the 1st, 2nd, 3rd and 4th gears rotate freely over the splines outer surface. Two sleeves are set on the splines of the main shaft, the gears are connected with the shaft by means of the gearshift sleeve. Involutes teeth are threaded on the outer surface of the engagement sleeve of the 1 st and 2nd gears. The gears are lubricated through labyrinth cavities in the casing, axial and radial bores in the shaft. The gear of the kick-starter has an additional small rim. The intermediate gear is installed on the neck of the bracket that travels in the Longitudinal direction of the shaft. Bronze bushings are pressed into the gear holes of the kick-starter, intermediate and 1 st gear of the main shaft. The kick-starter consists of shaft with pawl, the kick lever, return spring and kick-starter gear. The shaft is supported by the bushings provided in the gearbox casing.
The gear shift mechanism.
Gear shifting is performed in sequence. Downshifts are made by pushing down front of the gearshift lever, while up shifts are made by pushing down on the rear of the gearshift lever arm. The reverse gear engagement mechanism consists of quadrant with a shaft with the reverse gear engagement lever secured on it, together with an intermediate gear set on the bracket. The intermediate gear travels along the shaft, from the reverse gear engagement quadrant. When the reverse gear is engaged, the intermediate gear travels with the bracket along the shaft and connects the small rim of the starting gear with the rim of the sleeve engaging the 1st and 2nd gears on the main shaft. The reverse gear must be engaged from neutral. When the reverse gear engagement lever is returned to its initial position, the gear shift mechanism is set into the neutral position.
The driveshaft incorporates a flexible joint, the driveshaft and the universal joint. The flexible joint is a rubber-coupling sleeve. The propeller shaft is aligned by means of the ball end of the main shaft that enters the socket in the front end of the propeller shaft.
Brakes should be "bedded in" during the initial running in period. Speeds during this period should not exceed 70 km/h with sidecar attached, 90 km/h without sidecar (see "Speeds Recommended for Running in" table). Follow bedding in procedures carefully. Make approximately 100 stops using 75% of full braking power. This can be done over several periods and need not be done in one session. Choose an area with clean, dry pavement and no obstructions. Travel in a straight line and apply both the hand (front) brake as well as the foot (rear) brake. After burnishing the brake shoes, adjust your brakes on each wheel to reduce the gap between shoes and drums. This procedure will ensure maximum braking performance during the running-in period and is essential before raising your top speed, after your CJ750 has been carefully run in.
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