19
2020-03
What are the causes of crankshaft damage in motorcycles?
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During motorcycle operation, we often encounter numerous factors that can lead to damage to the crankshaft and crankpin. So, what are the common causes of crankshaft failure? There are many reasons, and today we’ll examine three of the most frequent ones:
(1) The main bearings and connecting‑rod bearings have suffered repeated scorching; as the load‑carrying capacity at the affected areas diminishes, the shaft exhibits frequent radial runout. Furthermore, after scorching occurs at the root, residual stresses are altered, leading to fracture between the crankpin root and the crank arm.
(2) Excessive clearance between adjacent main bearings—particularly between the rear two and the front two—often leads to fracture at the root of the connecting‑rod journal of cylinders 2 and 5 (taking a six‑cylinder engine as an example). This is because, with the flywheel at the rear and the pulley at the front, the crankshaft experiences excessive end loads, resulting in frequent radial runout. Combined with the impact forces generated during operation of the front and rear cylinders, this ultimately causes the crank arm to break.
(3) Excessive wear of the main bearings, coupled with prolonged looseness, results in fracture occurring in the rear half of the crankshaft.
The three factors mentioned above are common causes of crankshaft damage in motorcycles. As these examples show, many issues stem from inadequate maintenance. Going forward, it’s essential to pay close attention to engine upkeep when operating your motorcycle.
Xiexiang Machinery,Motorcycle crankshaft
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