The valve clearance usually changes due to the wear and deformation of the parts of the valve train. If the clearance is too large, the valve lift will be insufficient, causing insufficient intake, incomplete exhaust, and abnormal noise. If the clearance is too small, the valve will not close tightly, and it will cause air leakage. It is easy to ablate the working surface of the valve and the valve seat. Therefore, in the use process of the car and the maintenance, the valve clearance is carefully and meticulously specified by the original factory. Check and adjust the gap to ensure the normal operation of the engine.
The inspection and adjustment of the valve clearance is performed when the valve is completely closed and the valve is held up and falls on the cam base circle position. When adjusting, the simple and quick two-time adjustment method is generally adopted. First find the top dead center of the compression end of the first cylinder piston, adjust half of the valves, and then rotate the crankshaft one week to adjust the remaining half of the valve clearance. Therefore, how to determine the order of adjustable valves has become the key to the problem. Many experienced masters have compiled formulas for common models based on their years of experience. For example, the valve of a cylinder at the compression top dead center is checked from front to back: EQ6100-1 and CA6102 are both 1-2-4-5-8-9, and BJ492Q is 1-2-4-6, and then rotate the crankshaft one revolution. , Adjusting all remaining valve clearances.
Due to the complex and changeable engine mechanism, it is very difficult to close memory. Some people use the cylinder-by-cylinder adjustment method, that is, when the piston is at the top dead center of the compression end, check and adjust the cylinder’s intake and exhaust valve clearance. When using this method to adjust, the crankshaft is cranked many times and the work efficiency is low. Here is a simple and feasible method for confirming the adjustability of the valve clearance, that is, the “double row no entry method”. Among them, <double> means that the clearances of the intake and exhaust valves of the referenced cylinder are adjustable, <row> means that only the clearances of the exhaust valves of the referenced cylinder are adjustable, and <no> means that the clearances of the intake and exhaust valves are not adjustable. Refers to the adjustable clearance of the intake valve of the cylinder.
Double-row operation method
1 First divide the working sequence of the engine into two groups
2 For the first time, turn the piston of one cylinder to the top dead center of the compression end, press double, row, no, and adjust the half of the gap.
3 The second time, the crankshaft rotates one circle, the cylinder reaches the top dead center of the compression stroke, still press double, row, no, adjust the remaining half of the gap
4 Determine the throttle and exhaust valve.
<1> It can be determined according to the valve and the corresponding airway.
<2> Turn to the crankshaft to observe and confirm. The method is: when the piston of the first cylinder is at compression top dead center, rotate the crankshaft and observe the two valves of one cylinder. The exhaust valve moves first and the intake valve moves later. And make a mark on a kind of valve. Then check each cylinder in the order of ignition, and mark the valve with the same name as the first cylinder.
5 Determination of the top dead center of a cylinder compression
<1>The method of judging the fire head: record the position of the high-voltage line of the next cylinder, open the distributor cover, and rotate the crankshaft. When the fire head is opposite to the position of the high-voltage line of the first cylinder, it means that one cylinder is at the top dead center of compression.
<2> Reverse thrusting method: Rotate the crankshaft and observe that the exhaust valve of cylinder 6<4> which is in the same position as the connecting rod journal of the first cylinder crankshaft opens and closes gradually until the intake valve starts to act, 6<4> The cylinder is at the top dead center of the exhaust valve, that is, one cylinder is at the top dead center of compression.