Crankshaft; Main Journal Diameter Undersize; Crankpin Journal Diameter Undersize; Main Bearing And Connecting Rod Bearing - Mazda MX-5 1990 Workshop Manual

B
8-58
INSPECTION I REPAIR
05UOBX·163
Ll
1
x
t
ffiy
t
05UOBX·164
CRANKPIN
MAIN JOURNAL
05UOBX·165
"
DIMENSION
R~
1.5mm (0.06 in)
05UOBX·166
05UOBX·167
CRANKSHAFT
1. Check the journals aAd pins for damage, scoring, and oil
hole clogging.
2. Set the crankshaft on V-blocks.
3. Measure the crankshaft runout at the center journal.
Replace the crankshaft if necessary.
Runout: 0.04mm (0.0016 in) max.
4. Measure each journal diameter in X and Y directions at two
points.
Main journal
Diameter: 49.938-49.996mm (1.9661-1.9668 in)
Out-ot-round; 0.05mm (0.0020 in) max.
Crankpin journal
Diameter: 44.940-44.956mm (1.7693-1.7699 in)
Out-ot-round; 0.05mm (0.0020 in) max.
Caution
• Do not remove the fillet roll area R when grinding.
5. If the diameter is less than the minimum, grind the journals
to match an undersize bearing.
Undersize bearing;
0.25mm (0.010 in), 0.50mm (0.020 in),
0.75mm (0.030 in)
Main journal diameter undersize
mm (in)
Bearing size Journal diameter
0.25 (0.010) undersize 49.704-49.708 (1.9568-1.9570)
0.50 (0.020) undersize
49.454-49.458 (1.9470-1.9472)
0.75 (0.030) undersize 49.204-49.208 (1.9372-1.9373)
Crankpin journal diameter undersize
mm (in)
Bearing size Journal diameter
0.25 (0.010) undersize 44.690-44.706 (1.7594-1.7601)
0.50 (0.020) undersize 44.440-44.456 (1.7496-1.7502)
0.75 (0.030) undersize
44.190-44.206 (1.7398-1.7404)
BEARING
Main Bearing and Connecting Rod Bearing
1. Check the main bearings and the connecting rod bearings
for peeling, scoring, and other damage.