Taking up bearings is not properly a job for the amateur. Nevertheless, there are times when it is well to know the procedure. Crank-pin bearings are frequently fitted with shims A A of thin brass or copper (Fig. 327) and a rough adjustment may be made by taking out one or two shims on each side, being careful to remove the same aggregate thickness from both sides. If it is found that taking out the thinnest shim leaves the bearing tight, shims may be cut from paper to make the bearing turn freely. In case there are no shims, it is necessary to file down the flat surfaces B B of the cap. This must be done with great care, otherwise one end or one corner may be filed too much and the cap sprung, or made to bind on the crankpin. After filing a little, the cap must be bolted on, and the shaft turned to ascertain whether enough has been taken off.

The wear of a crankpin is chiefly in the top half. The wear of the main bearings is in the bottom halves, which are usually removable caps. It follows that to refit the main bearings, the bottom caps are simply raised to bring the shaft up against the top halves of the bearings. Fig. 328 shows a crankshaft with both end bearings removed, the crankcase wall and the upper bearings being indicated in section, and the lower half of the crankcase removed. The shaft is held up by the central cap A, and the front bottom cap B is shown in perspective. If the main bearings have shims similar to A A, Fig. 327, it is only necessary to take out whatever thickness is necessary to make the bearing tight. If there are no shims, the flat faces C C must be filed. A bearing taken up in this manner is seldom a first-class job, because it rarely results that the shaft has a full bearing all over the surface. Generally the shaft is out of line, or it is cut, or the bearing is cut; and taking up as above described simply enables the car to be run a few hundred miles farther, to save putting it in the shop at an inconvenient time.

Fig. 327 - Taking up crankpin bearings.

Fig. 328 - Tightening the crankshaft bearings.