Annually or every 20,000 km.
This procedure does not apply to the M10 engine, which has automatic governors.
Valve clearances can be checked both hot and cold, but keep in mind that the values obtained should differ depending on the temperature of the engine. If you are going to carry out the clearance check and adjustment procedure with the engine warm, you must start it, warm it up to normal operating temperature and then turn it off.
If valve clearances are adjusted when the engine is hot, be especially careful to avoid burns.
1. Remove the cylinder head cover from the engine (see part Repair work carried out without removing the engine from the car).
2. Rotate the engine until the #1 front piston is at top dead center (TDC) compression stroke (see part Repair work carried out without removing the engine from the car).
3. Check valve clearances for cylinder #1. The required clearances are given in Table of sizes and adjustment data at the end of the Guide.
4. Clearance is measured by inserting a feeler gauge of the required size between the end of the valve stem and the adjusting eccentric of the valve lever. The probe should pass into the gap with some resistance.
5. If the gap is too large or too small, loosen the lock nut, insert a thick metal wire hook and turn the eccentric until the desired gap is reached.
6. Once the gap is set, tighten the locknut securely while holding the eccentric in position with the hook. Check the gap again - sometimes it changes slightly after tightening the lock nut. In this case, adjust it to the desired value.
7. On M10 engines, the valves are adjusted in the order of cylinder operation, namely 1-3-4-2. After adjusting the valves of the first cylinder, turn the crankshaft half a turn (180°), then check and adjust the valves on the third cylinder. Repeat the procedure on the remaining cylinders.
8. On M20 and M30 engines, the valves are also adjusted in the order of cylinder operation, namely 1-5-3-6-2-4. After adjusting the valves of the first cylinder, turn the crankshaft a third of a turn (120°), then check and adjust the valves on the fifth cylinder. Repeat the procedure on the remaining cylinders.
9. Install the cylinder head cover (use a new gasket) and tighten the mounting nuts evenly and securely.
10. Start the engine and check for oil leaks between the cylinder head cover and cylinder head.