Valve Clearance: Adjustments

63 Cap nut
63a Counternut

NOTE: Check valve clearance with engine cold or warm and adjust, if required.
During adjustment, check cap nut and counternut for tight seat and wear.
Also check valves which are not in need of adjustment.
Renew cap nuts and counternuts in the following cases:






Height of counternut (A) below 5 mm (H). New counternuts (B) have a height of 6 mm.






Counterlocking surfaces of nuts badly worn (arrows).

In such cases, check threads on valve stem and also replace valves, if required.






Check camshafts made of malleable iron (code number 00) for wear. Formation of excessive flats on cam (arrow) may result in loosening of counterlocked nuts. If flats show up, renew camshaft, rocker arm, valve springs, as well as cap nuts and counternuts. Also check valves and replace, if required.

On camshafts made of chilled cast iron (code number 05 and 08) a slight formation of flats is possible, but flats will not increase and are therefore technically insignificant.

Salt bath-nitrited counternuts (formerly phosphatized) are installed to improve operational reliability.

When stocks are used up, only the modified counternuts will be available.

The part No. has not been changed.






Production breakpoint: October 1983






Model 126.120






Model 123






Model 126.120

Adjustment
1 Disconnect regulating linkage to remove cylinder head cover. Pull out locking eye of longitudinal regulating shaft (arrow).

On models 116.120 and 123, pull longitudinal regulating shaft out of rubber mount in forward direction and remove in rearward direction.

On models 123 with automatic transmission 722.303 (W 4 A 040) and 126.120, pull off central plug for vacuum lines (71) or vacuum lines. Disconnect Bowden wire, compress black plastic clip (arrow) and pull Bowden wire out of holder in rearward direction.






2 Check valve clearance between slide surface of rocker arm and cam base circle of camshaft (arrow). Tip of cam should be vertical in relation to rocker arm.

Valve clearance is correctly set when pulling of slip gage blade requires some effort.






Observe layout of intake and exhaust valves.






The engine can be rotated as follows:

a) With tool combination at crankshaft front

Attention! Do not rotate engine at fastening bolt of camshaft sprocket. Do not rotate crankshaft in reverse.

b) Using starter and remote starter switch Connect remote starter switch to terminals 30 and 50 on starter. Battery positive can be used in place of terminal 30.





Model 123: At right on wheel house.






Model 126.120: On frame side member.






3 Place holding wrench on valve spring retainer.






4 Loosen cap nut while applying counterhold to counternut on valve by means of valve adjusting wrench.
5 Adjust valve clearance by turning cap nut.
6 Following adjustment, secure cap nut with counternut (torque reference value 20 - 30 Nm).
7 Check valve clearance once again.