1. Make sure the engine is cold.
2. Remove the spark plug.
3. Remove the valve cover.
4. Locate the intake and exhaust valves. The intake valve is on the left side of the cylinder, and the exhaust valve is on the right side.
5. Use a feeler gauge to measure the clearance between the valve stem and the rocker arm. The clearance should be 0.004-0.006 inches (0.10-0.15 mm) for the intake valve and 0.006-0.008 inches (0.15-0.20 mm) for the exhaust valve.
6. If the clearance is too small, use a wrench to loosen the locknut on the rocker arm. Then, turn the adjusting screw to increase the clearance.
7. If the clearance is too large, use a wrench to tighten the locknut on the rocker arm. Then, turn the adjusting screw to decrease the clearance.
8. Once the clearance is correct, tighten the locknut.
9. Repeat steps 5-8 for the exhaust valve.
10. Replace the valve cover.
11. Replace the spark plug.
12. Start the engine and check for any unusual noises.
