Valve abnormal noise is a typical fault of the engine valve system, which is often caused by metal knocking and can be easily confused with abnormal noise from the crankshaft and timing system. If not diagnosed in a timely manner, it can exacerbate wear on components such as valves and rocker arms, affecting engine power and smoothness. The core of rapid diagnosis is to "listen to the sound, observe the working conditions, and determine the location", combined with simple operations to accurately locate faults. The following are detailed diagnostic methods.

The axial clearance of the crankshaft is a key precision indicator for engine assembly, which refers to the amount of movement of the crankshaft along the axis direction in the cylinder block. A clearance that is too large or too small can affect engine operation. A clearance that is too large can cause crankshaft movement and abnormal noise, while a clearance that is too small can cause jamming due to thermal expansion and contraction. The following are general inspection methods suitable for various types of fuel engines, which are easy to operate and can accurately determine whether the clearance meets the standard.

The crankshaft oil seal is a key component of the engine sealing system, divided into a front oil seal and a rear oil seal, which seal the front and rear ends of the crankshaft respectively. Once there is oil leakage, it can cause oil loss, engine noise, and even chain failures such as belt slippage and component wear. The solution to crankshaft oil seal leakage should follow the principle of "locating the leakage point first, and then treating it accordingly". The following are general solutions that are suitable for most fuel engine models.

The core of crankshaft repair is to choose the right method based on the degree of wear. Minor wear can be repaired by electroplating or small-sized grinding, while moderate to severe wear should be repaired by grinding or welding after grinding. Regardless of the solution, strict inspection of the dimensional tolerances and fit clearances of the shaft neck is required after repair, and the repaired crankshaft must be adequately lubricated before installation to avoid the recurrence of wear and tear faults.

The core of crankshaft installation lies in "precision" and "standardization", and any negligence in detail may lead to subsequent engine failures. Strictly following the above precautions is necessary to ensure the assembly accuracy of the crankshaft and lay the foundation for the stable operation of the engine.

The crankshaft is the core transmission component of the engine, which is subjected to periodic impact loads and rotational centrifugal forces for a long time, and is prone to various types of damage. If not repaired in a timely manner, it can cause engine shaking, power decline, and even complete machine scrapping. Mastering the common types of crankshaft damage and maintenance methods is the key to ensuring stable engine operation.

We will take a four stroke engine as an example to analyze its core components and functions.