How to Adjust Valve Clearance?
2 Answers
Valve clearance adjustment method: After determining the position of a cylinder's piston at the compression top dead center according to the cylinder firing order, the intake and exhaust valve clearance of that cylinder can be adjusted. Once adjusted, rotate the crankshaft and gradually adjust the valve clearance of other cylinders in the same manner. When the engine is running, the valves expand due to temperature rise. If there is no clearance or the clearance is too small between the valve and its transmission components in the cold state, the thermal expansion of the valve and its transmission components in the hot state will inevitably cause the valve to not close tightly. The function of the valve is to specifically input air into the engine and discharge the exhaust gas after combustion. From the engine structure, it is divided into intake valve and exhaust valve. The intake valve is responsible for drawing air into the engine to mix with fuel for combustion; the exhaust valve is responsible for discharging the burned exhaust gas and dissipating heat.
Last time I helped a friend adjust the valve clearance, it felt like solving a puzzle. First, you have to make sure the engine is cold—never work on it while hot because thermal expansion affects measurements. I used a feeler gauge—that slender strip measuring tool—to locate the gap between the valve tip and rocker arm. Then, I loosened the adjustment nut and carefully turned the adjusting screw until the feeler gauge could slide in with slight resistance, neither too tight nor too loose. Throughout the process, I followed the cylinder sequence in the manual step by step, avoiding skipping around to prevent missing any adjustments. After measuring, I double-checked to ensure the clearance was within the specified range, say around 0.15 to 0.25mm. Too small a gap would prevent the valve from sealing properly, causing the engine to overheat; too large would lead to ticking noises and increased fuel consumption. As for tools, basically a wrench and a set of feeler gauges are enough, but beginners might want to keep a notebook for recording parameters. Regular checks every 20,000 kilometers can prevent major issues—don’t wait until the engine blows to regret it.
