What is the most suitable engine valve clearance?

Valve clearance adjustment method: 1, and the optimal valve clearance is 0.25mm According to the adjustment method of cylinders, that is, the ignition sequence of cylinders, after determining that the piston of one cylinder is at the compression top dead center position, adjust the valve clearance of the intake and exhaust of the cylinder, and then rotate the crankshaft to gradually adjust the valve clearance of other cylinders. 2. Make the piston of the first cylinder at the compression top dead center, and align the flywheel mark with the scribing line of the inspection hole. At this time, adjust the valves 1, 2, 4, 5, 8 and 9, and then let the crankshaft rotate once to compress the piston of the sixth cylinder. This is actually the adjustment of memory methods. 3. When adjusting, please tighten the adjusting screw, insert the exposure meter between the valve stem end and the rocker arm, pull it back and forth, and recheck it until it is correct again.