Motorcycle Body And Crank Connecting Rod

2. Body
The engine body is composed of three parts: the cylinder head, cylinder block, and crankcase. The cylinder head is made of aluminum alloy cast with heat dissipation fins. The new four stroke motorcycle engine adopts an overhead valve, chain drive, and overhead camshaft structure. The cylinder body material is mostly bimetallic (wear-resistant cast iron cylinder liner with aluminum heat dissipation fins) to achieve better heat dissipation effect. Some motorcycles use wear-resistant cast iron cylinder bodies, such as the Yangtze River 750 and Jialing JH70 models. In some small light motorcycles, such as the Yuhe YH50Q small displacement (50 cubic centimeters) engine, an aluminum alloy cylinder body with a 0.15 mm hard chromium layer on the inner wall is used. The crankcase is made of aluminum alloy die-casting and consists of a combination of left and right boxes. Some motorcycles have buffer blocks added between the heat dissipation characteristics to suppress the noise emitted by the vibration of the heat dissipation fins.
3. Crank connecting rod
The crankshaft of the motorcycle engine adopts a combination type, which is formed by pressing the left half crankshaft, right half crankshaft, and crankshaft pin. The main journals of the left and right half shafts are equipped with ball bearings to support the crankshaft on the crankcase. The two ends of the crankshaft are respectively equipped with flywheels, magnetos, and clutch driving gears. The connecting rod is of an integral structure, with a large end in a circular shape, and is equipped with a needle roller bearing and a crank pin assembly to form a crank connecting rod assembly. When installing the piston ring in a two-stroke engine, attention should be paid to aligning the opening of the piston ring with the positioning pin in the piston ring groove to prevent the piston ring from rotating in the groove, causing air leakage and scratching the intake and exhaust ports on the cylinder liner.