Inspect the outer surface of each cylinder for evidence of burn
and for scratch or groove marks. Minor flaws can be removed by
grinding with fine-grain sandpaper.
De-carbon the piston crown and ring grooves, using a soft-metal
scraping tool.
Ring clearance in the groove:
Using a thickness gauge (1), check each piston ring (2) in its
groove for side clearance and, if the limit stated below is exceed-
ed, measure the groove width and ring width to determine
whether the piston or the ring or both have to be replaced.
Piston ring end gap:
To measure the end gap, insert the piston ring (2) into the cylin-
der bore, locating it at the lowest part of the bore and holding it
true and square; then use a thickness gauge (1) to measure the
gap. If the gap measured exceeds the limit, replace the ring.
“a”: 120 mm (4.72 in.)
ENGINE MECHANICAL (F8B ENGINE)
6A-27
Item
Standard
Limit
Ring clearance
Top ring
0.03 – 0.07 mm
(0.0012 – 0.0028 in.)
0.12 mm
(0.0047 in.)
g
in the groove
2nd ring
0.02 – 0.06 mm
(0.0008 – 0.0024 in.)
0.10 mm
(0.0039 in.)
Piston ring
Top ring
1 47
1 49 mm (0 0579
0 0587 in )
Piston ring
thickness
2nd ring
1.47 – 1.49 mm (0.0579 – 0.0587 in.)
thickness
Oil ring
0.45 mm (0.0177 in.)
Ring
Top ring
1.52 – 1.54 mm (0.0598 – 0.0606 in.)
g
groove
2nd ring
1.51 – 1.53 mm (0.0594 – 0.0602 in.)
width
Oil ring
2.81 – 2.83 mm (0.1106 – 0.1114 in.)
Item
Standard
Limit
Top ring
0.15 – 0.30 mm
(0.006 – 0.012 in.)
0.7 mm
(0.028 in.)
Piston ring end gap
2nd ring
0.10 – 0.30 mm
(0.004 – 0.012 in.)
0.7 mm
(0.028 in.)
Oil ring
0.20 – 0.70 mm
(0.008 – 0.028 in.)
1.8 mm
(0.040 in.)
