Valve Clearance: Adjustments
Checking and adjusting valve clearanceSpecial tool required: P 213 Feeler gauge
Always check or adjust valve clearance when the engine is cold and outside temperature in the region of 20°C (68°F).
The prescribed clearances should be most carefully adhered to, and must be checked at recommended intervals. Check clearances with the feeler gauge only between the valve stem and the valve cap, which is in the form of a spherical socket.
Valve clearance with engine cold:
Intake: 0.1 mm (.0039")
Exhaust: 0.1 mm (.0039")
Inaccurate setting of valve clearances may have the following effects:
Insufficient clearance:
Burnang of valves or valve seats
Distortion of valve stems
Irregular running of engine
Alterations to engine timing.
Excessive clearance:
Increase in noise from valve gear
Rapid wear on valve gear components
Irregular running of engine
Alterations to engine timing.
The valves are correctly adjusted when each valve seats correctly with no undue play in the valve guides or pounding of valve stem ends.
Reground or returned valve seats will bed down while the engine is running. In this case valve clearances 0.15 mm (.0059") in excess of normal should be set for a half-hour engine test run.
Following the test run or before the performance of the engine is checked the valve clearances should be reduced to the normal values stated above.
Adjustment of valve clearances
It is desirable for valve clearances to be checked in the firing order 1-6-2-4-3-5. The piston of the appropriate cylinder must be at TDC, at which point both valves will be closed. TDC markings for each cylinder are to be found on the belt pulley.
Beginning with No.1 cylinder the crankshaft and belt pulley should be turned to the right until both valves of No.1 cylinder are closed, and the cylinder TDC marking (Z1) on the belt pulley coincides with the mark on the crankcase.
Proceed as follows:
1. Remove cylinder head cover.
2. Bring piston of cylinder to be adjusted to TDC on firing cycle.
3. Check valve clearance with feeler gauge.
4. Loosen adjusting screw hexagon nut.
5. Adjust clearance by turning adjusting screw with a screwdriver while holding nut steady. Check with feeler gauge.
6. Hold adjusting screw securely and tighten locknut.
7. Check that clearance has not altered.
8. Turn crankshaft by means of belt pulley until next mark is reached (120°).
9. While in this position, check clearance of valves in No.6 cylinder.
10. Turn crankshaft a further 120° until No. 2 cylinder is a TDC on firing cycle.
11. Repeat this procedure until all valves have been checked.
12. Replace cylinder head cover.