What is the cause of small shaft noise in one cylinder of an engine?

[VanJack]

Small shaft noise in a cylinder is related to the crankshaft bearing, connecting rod bearing, piston pin, and piston ring areas. The function of the engine crankshaft: The crankshaft is the main rotating mechanism of the engine, responsible for converting the up-and-down reciprocating motion of the piston into its own circular motion. The engine speed is essentially the speed of the crankshaft. The crankshaft bears the force transmitted by the connecting rod and converts it into torque, which is then output through the crankshaft to drive other engine accessories. Composition of the crankshaft: The crankshaft mainly consists of the crankshaft front end (or free end), connecting rod journal, main journal crank, balance weight, and crankshaft rear end flange (or power output end). The main journal is installed on the cylinder block, the connecting rod journal is connected to the big end hole of the connecting rod, and the small end hole of the connecting rod is connected to the cylinder piston, forming a typical crank-slider mechanism.