Using a set of feeler gauges, measure the clearance in the valve drive mechanism, which should be (on a cold engine):
- inlet valves: 0.26 - 0.34 mm;
- exhaust valves: 0.29 - 0.37 mm.
Compare the obtained values with the required ones.
Replace the tappets if the clearances between them and the camshaft lobes are outside the tolerances.
Measure the lifter thickness with a micrometer and repeat the procedure for lifters with out of tolerance valve clearances to match the lifter thickness.
