Examine the crank pin and main journal surfaces for signs of scoring or scratches, and check the ovality of the crank pins at different positions with a micrometer; if they are out of round beyond specified limits, regrinding is necessary, as well as for any scores or scratches present. If regrinding the crankshaft and fitting new bearings is required, a local BMW garage or engineering works can determine how much metal to grind off and the size of new bearing shells, along with the restoration of surface hardening (Nitriding) of the bearing surfaces. Main bearing clearances can be established using a strip of 'Plastigage' between the crankshaft journals and the main bearing/shell caps, tightening the bearing cap bolts to a torque of 45 lb/ft (62 Nm) before removing the cap to compare the flattened Plastigage strip with the provided index. Temporarily refit the crankshaft to the crankcase with the upper halves of the shell main bearings in place, fitting only the no.3 main bearing cap with the shell bearing and tightening the securing bolts to 45 lb/ft (62 Nm) torque; check the end float with a feeler gauge, and if it is outside the specified tolerance, renew the no. 3 bearing shells. Finally, check the pilot ball race in the center of the crankshaft rear flange for wear or damage, and if necessary, extract it. When installing new pilot bearing components, pack the bearing with high-melting point grease and impregnate the felt ring with hot tallow, ensuring the marking on the cover plate faces outwards before tapping the retainer into place until it seats.
