Maintenance - Minor Service

5.2 Adjusting the valve clearances with service tools

The shims are changed by pressing down the cam follower (tappet bucket) using a specially-shaped depressor lever, BMW part number 11 1 721, and holding it down using a spacer, BMW tool number 1 1 1722; the shims can then be extracted using a pointed instrument or a pair of large tweezers or needle-nosed pliers. lf these tools are available, proceed as follows.

Position the cam lobe so that it is pointing directly away from the valve to be adjusted, then rotate the cam follower so that the notch in its raised edge faces in (towards the center of the head); later models have followers with two notches to facilitate this. Insert the depressor lever under the camshaft next to the lobe, check that it bears fully on the shim, then press the handle upwards (intake valve) or downwards (exhaust valve) until it touches the cylinder head wall, thus pressing the valve assembly into the cylinder head. Fit the spacer so that it locks securely under the camshaft with its foot bearing squarely on the edge of the follower i.e. clear of the shim. It is essential that the spacer rests squarely on the edge of the follower, or it may slip and lock the follower in place by raising a burr on the cylinder head.

Using a pointed instrument, prise the shim out of its recess and withdraw it, noting the number painted on its underside. Shims are available in increments of 0.05 mm (0.0020 in) in a range of thickness from 2.00 - 3.00 mm (0.0787 - 0.1181 in). To adjust a valve's clearance, note the thickness of the present shim; if the painted number has been polished away measure the shim with a micrometer or vernier caliper or similar and record it.

If the measured clearance was too small, select the next size thinner shim, install it and recheck the clearance; if the clearance was too large a thicker shim must be installed. The clearance does not usually require adjusting by more than one shim size. Note that as a picture of the valve gear is built up it may be possible to reduce the cost by swapping shims between valves so that the smallest number of new shims has to be purchased.

Refit the shims ensuring that their painted numbers are facing downwards so that they are not polished away by the cam lobe, and that each shim is seated fully in its recess. Refit the depressor lever and push down the valve assembly, withdraw the spacer and slowly move the depressor lever to release the cam follower. Rotate the follower through a full circle to ensure that the new shim is securely seated at all points, then measure the clearance again and record it. Repeat the process for all other valves.

When all clearances have been checked and adjusted, turn the engine over several times to settle all components (if the starter motor is used be careful to protect the ignition system components as described in Chapter 6 - Ignition), then recheck all clearances to ensure that none have altered through shims settling. If all is well, refit the cylinder head cover as described in Chapter 1 - Engine.

Note that if the clearances required significant alteration, the throttle butterfly assembly synchronization should be checked as described in Chapter 5 - Fuel & Oil.

Note: Always record the date and mileage of each check and all relevant information i.e. original clearance, original shim thickness, news him thickness and final clearance. In this way an extremely accurate picture can be obtained of the rate of wear of the valve gear, until it is almost possible to predict when a particular valve will need adjusting. Obviously if the pattern changes suddenly, the reason should be investigated before serious trouble is encountered. Note that with this system of valve clearance adjustment wear of the valve gear is minimal and it is more likely that thinner shims will be required to compensate for wear at the valve seat. Once the shins have been properly set up after running in, adjustment should be only rarely required, thus offsetting the extra expense of the system.

Valve clearance adjustment requires special tools if camshafts are not to be removed

Hook depressor lever under camshaft and press
lever downwards for exhaust ..... 

..... or upwards for intake until valve assembly is depressed sufficiently for spacer to be fitted

Shim can be prised out via notch in cam follower rim - - check spacer bears securely on follower only

Number painted on shim underside indicates thickness, in this case 2,05 mm

Measure shim thickness with caliper or micrometer if number is erased

Fit shims with number downwards and check that they are seated fully in their followers