Measure the journals with an outside micrometer as shown in Figure 5.18. Check for both taper and out-of- round. When checking taper, measure each end of the journal. When checking out-of-round, take measurements at 900. There are four places where measurements have to be taken. These are shown in Figure 5.19.
Crankshaft and bearing specifications
| CRANKSHAFT ITEM || SPECIFICATIONS |
| Crankshaft runout at centre || 0.06 mm |
| Main-journal diameter || |
| Main-journal out-of-round || 0.04 mm |
| Crankpin diameter || |
| Crank-pin taper and out-of-round || 0.04 mm |
| || 0.030—0.050 mm |
| Crankshaft end-play || 0.10—0.30 mm |
| || 0.02—0.06 mm |
| Connecting-rod big-end side || |
| clearance || 0.10—0.35 mm |
| || |
| Flywheel run-out || 0.20 mm |
A special crankshaft grinder is used to grind crankshaft journals (Figure 5.20). The grinder is fitted with chucks at each end which support the ends of the crankshaft. During grinding, the shaft is rotated and the grinding wheel of the machine is used to accurately grind each journal. This is done to a specified size to suit undersize bearings.
When a crankshaft is removed from the engine, it should be cleaned in a suitable solvent, particularly the oil passages. To prevent rusting, the journals should be oiled immediately after they have been cleaned.
A crankshaft that has been ground needs to be cleaned properly to remove abrasive and metal particles that are the result of grinding.