How to adjust the 24 valves of Yuchai 6M engine?
2 Answers
First, rotate the crankshaft to position the piston of the first cylinder at the compression top dead center. For a 4-cylinder engine, first adjust the intake and exhaust valves of cylinder 1, the exhaust valve of cylinder 3, and the intake valve of cylinder 2. Then, rotate the crankshaft 360 degrees (i.e., one full turn) to adjust the remaining valves.
I've been repairing cars for many years and have seen plenty of issues with the Yuchai 6M engine. Adjusting those 24 valves is no small task. You must let the engine cool completely before starting, as thermal expansion alters the clearances. First, remove the valve cover and use a feeler gauge to measure each valve's clearance. The Yuchai manual specifies recommended values, typically 0.25 to 0.35 mm depending on the model. Loosen the adjustment screw with a wrench, then retighten to the specified clearance and double-check. Never attempt to adjust all valves simultaneously - work methodically one by one. Rotate the crankshaft to find top dead center, ensuring you're working on the correct cylinder. With 24 valves, mistakes are easy - beginners should take notes. Proper adjustment reduces fuel consumption and noise, but inexperienced mechanics should visit professional shops since valves are critical components. Incorrect adjustment may damage valves, causing oil burning and costly repairs. During routine maintenance, inspect valve clearances and consider adjustment every 50,000 km to ensure engine longevity.
