1. Remove the spark plug and cylinder head cover.
2. Rotate the crankshaft until the piston is at top dead center (TDC) of the compression stroke. This can be done by inserting a screwdriver into the spark plug hole and watching for the piston to rise to the highest point in its travel.
3. Use a feeler gauge to measure the clearance between the valve stem and the rocker arm. The clearance should be 0.002 inches (0.05 mm) for the intake valve and 0.004 inches (0.10 mm) for the exhaust valve.
4. If the clearance is not within specifications, use a flat-head screwdriver to turn the adjuster screw until the clearance is correct.
5. Repeat steps 3 and 4 for the other valve.
6. Reinstall the spark plug and cylinder head cover.
Yamaha Moto-4 350cc Valve Adjustment Procedure
1. Remove the fuel tank, seat, and air filter cover.
2. Rotate the crankshaft until the piston is at TDC of the compression stroke (see step 2 above).
3. Remove the valve clearance cover.
4. Use a feeler gauge to measure the clearance between the valve stem and the rocker arm. The clearance should be 0.006 inches (0.15 mm) for the intake valve and 0.008 inches (0.20 mm) for the exhaust valve.
5. If the clearance is not within specifications, use a wrench to turn the adjuster nut until the clearance is correct.
6. Repeat steps 3 and 4 for the other valve.
7. Reinstall the valve clearance cover, air filter cover, seat, and fuel tank.
