Undersized Main Bearing Selection

Undersized Main Bearing Selection





1. If new standard bearings do not produce the correct oil clearance, regrind the crankshaft to a finished diameter of 64.732 - 64.750 mm (2.5485 - 2.5492 inch) and install 0.25 mm (0.0098 inch) undersized bearings. Undersized bearings are available in 5 sizes (tolerances) differing in thickness in the center of the bearing.
2. Undersized bearings are distinguished from standard size bearings by a double paint mark (1).
- Green and red paint indicates a bearing thickness of 2.618 - 2.622 mm (0.1031 - 0.1032 inch).
- Black and red paint indicates a bearing thickness of 2.621 - 2.625 mm (0.1032 - 0.1033 inch).
- Red paint only indicates a bearing thickness of 2.624 - 2.628 mm (0.1033 - 0.1034 inch).
- Yellow and red paint indicates a bearing thickness of 2.627 - 2.631 mm (0.1034 - 0.1035 inch).
- Blue and red paint indicates a bearing thickness of 2.630 - 2.634 mm (0.1035 - 0.1036 inch).





3. Measure the reground crankshaft journals for out-of-round.
Maximum Out-of-Round 0.01 mm (0.0004 inch)
4. Measure the reground crankshaft journals for taper.
Maximum Taper 0.01 mm (0.0004 inch)
5. Measure the reground crankshaft journals for size.
6. Refer to the undersized main bearing selection table in Specifications. Using the intersection of the measured journal size and the letters on the lower crankcase select the correct sized bearing from the table. Measure the oil clearance. If the oil clearance is incorrect install the next thicker bearing and recheck the oil clearance.