After the engine starts running, it is necessary to overcome the friction resistance generated between the moving parts, to overcome the friction resistance is easy to lead to part of the power loss and wear of the parts, affecting the service life of the engine, in order to reduce friction and power loss, the contact surface of the engine moving parts must be lubricated.

The lubrication system of a four-stroke engine is: The engine runs with a motor oil pump, and the lubricating oil is transported to the clutch, bearings, main and auxiliary shaft gears through the oil channel, pressurized by the crankcase, transported to the cylinder head, the camshaft of the lubricating valve mechanism, the rocker arm, the valve timing chain and other components, and the crankshaft connecting rod big head bearing is lubricated through the right crankshaft oil channel, and the cylinder block and piston assembly are lubricated by splash.

Finally, through the role of the centrifugal oil filter, the coarse filter of the oil filter screen or the filter circulation of the oil filter paper flow back to the axle box. When the crankcase lubricating oil is insufficient, the oil passage is blocked, and the lubricating oil filter element fails, the engine lubrication road will be blocked, resulting in normal oil circulation, engine lubrication system failure, noise, overheating phenomenon.

When replacing the crankcase lubricating oil, check and clean the debris on the filter net in the oil drain bolt; Check whether the oil filter installed in the crankcase is blocked by oil and debris (50~100mL four-stroke engine); Check the paper oil filter paper installed on the crankcase for failure (125~250mL) four-stroke engine).

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