The size of the piston skirt between the cylinder and the cylinder is the largest diameter of the main and secondary thrust surface of the piston skirt. The difference between the inner diameter of the cylinder and the size of the skirt is the gap between the cylinder and the skirt. This is a very important fit gap between the engine and the engine, and the failure of the cylinder may occur if there is a difference of the difference between the cylinder and the cylinder. The skirt size is measured in detail with the inner diameter micrometer. When the skirt size is not measured, the diameter of the skirt can be measured along the main and sub thrust surface. The maximum diameter is the skirt size. The common aluminum piston and cast iron cylinder liner, the standard measurement room temperature is 20 C, every rise (drop) 10 degrees C, can reduce (increase) about 0.01 millimeters of the cylinder clearance. When opening the gap and replacing the piston ring, the piston ring opening gap must be checked with a feeler gauge. For worn cylinders, when opening clearance, the ring should be placed at the lowest wear point near the bottom stop to prevent the opening from being killed. To check whether the opening gap exceeds the allowable limit, the ring should be placed near the top dead center. After boring the cylinder bore, check the opening clearance is not limited by position. The clearance between piston ring and backlash piston ring is measured by feeler gauge. The side gap is too small to cause snap ring and cylinder drawing. When the air leakage is too large and the oil is oiled and severely punished, the piston ring and the shore are broken. Replacing the new piston ring should measure the side clearance is too small; in the piston ring, check whether the side gap exceeds the allowable limit, especially the first ring. The top stop of the cylinder is easy to wear out into a step. The cylinder head must be machined and the steps should be trimmed, otherwise the first ring gap will increase sharply. There is no backlash in the ring slot in the ring and the cylinder can be pulled. The ring should be pressed into the bottom of the ring groove, and the outer surface of the ring should be lower than the outer surface of the ring bank, otherwise it can not be mounted into the slot.