活塞敲打气缸的主要原因如下：活塞和气缸壁之间的间隙太大。WD615系列发动机的活塞裙和气缸之间的标准间隙为0.143-0.182，磨损极限为0.35-0.40。

The main reasons for the piston striking the cylinder are as follows: the gap between the piston and the cylinder wall is too large. The standard clearance between piston skirt and cylinder of WD615 Series engine is 0.143-0.182, and the wear limit is 0.35-0.40.

发动机运转一段时间后，气缸活塞磨损并且润滑不良。活塞和气缸之间的匹配间隙由于磨损而增大，并且在气环中略微出现严重的台阶，从而导致活塞撞击气缸。声音异常。经过一段时间的使用后，活塞裙和缸体严重磨损，严重倒圆并冲击缸体。

After the engine runs for a period of time, the cylinder piston is worn and the lubrication is poor. The matching gap between the piston and the cylinder increases due to wear, and a serious step appears slightly in the first gas ring, resulting in the piston hitting the cylinder. The sound is abnormal. After a period of use, the piston skirt and cylinder block are seriously worn, seriously rounded and impacted.

每个连杆由于各种原因而变形，导致活塞偏心，间隙变大，气缸受到撞击。活塞爆震缸会导致发动机油耗过多，发动机油耗降低，油耗降低和经济效益提高。当活塞严重撞击汽缸时，它将拉动活塞并使汽缸破裂，从而导致连杆断裂并损坏汽缸体。

Each connecting rod is deformed due to various reasons, resulting in eccentric piston, larger clearance and impact on the cylinder. Piston knock cylinder will lead to excessive fuel consumption, low fuel consumption and economic benefit. When the piston hits the cylinder seriously, it will pull the piston and break the cylinder, which will cause the connecting rod to break and damage the cylinder block.

判断活塞爆炸的方法：

The method to judge piston explosion is as follows

（1）逐缸切削油：逐缸方法用于确定喷砂缸的位置。如果将油切到某个气缸，声音会大大降低或消失，并且在恢复供油时可以清晰听到。“喀哒”声表示气缸活塞撞击气缸。

(1) Cylinder by cylinder cutting oil: the cylinder by cylinder method is used to determine the position of the sandblasting cylinder. If the oil is cut to a certain cylinder, the sound will be greatly reduced or disappeared, and can be heard clearly when the oil supply is restored. A "click" sound indicates that the piston of the cylinder hits the cylinder.

（2）为了进一步确认气缸活塞被撞，可以将气缸的喷油器卸下，向气缸中添加少量的CD级增压油（密封件），安装喷油器，并装上发动机开始。敲击声消失或减弱。手术后，再次有敲门声，毫无疑问，它敲击了汽缸的活塞。

(2) In order to further confirm that the cylinder piston has been hit, the fuel injector of the cylinder can be removed, a small amount of CD grade booster oil (seal) can be added to the cylinder, the fuel injector can be installed, and the engine can be installed. The knocking sound disappears or weakens. After the operation, there was another knock on the door, which undoubtedly knocked on the piston of the cylinder.

对于活塞缸，可以使用以下方法：

For piston cylinders, the following methods can be used:

（1）发动机启动后，在低温下运转时，发动机会发出爆震声。温度恢复正常后，声音消失，可以暂时进行处理，而无需进一步处理。

(1) After the engine starts, when it runs at low temperature, the engine will make a knock sound. After the temperature returns to normal, the sound disappears and can be processed temporarily without further processing.

（2）当发动机温度正常时，会有明显的爆震声。尽量避免高速操作，拆卸和维护。

(2) When the engine temperature is normal, there will be obvious knock sound. Avoid high speed operation, disassembly and maintenance as far as possible.

（3）拆下气缸盖并拔出活塞后，发现气缸严重掉落或变形，或活塞与气缸之间的间隙过大，应将气缸套，活塞和活塞环拉紧。更换。

(3) After removing the cylinder head and pulling out the piston, if the cylinder is seriously dropped or deformed, or the gap between the piston and the cylinder is too large, the cylinder liner, piston and piston ring should be tightened. Replace.

（4）如果发现（混凝土搅拌机）的连杆变形，则应尽可能更换。

(4) If the connecting rod of (concrete mixer) is found to be deformed, it should be replaced as far as possible.