Yanmar 3JH4BE - Page 122

5. Inspection and Servicing of Basic Engine Parts
106
(1) Measuring the rings.
Measure the thickness and width of the rings, and the
ring-to-groove clearance after installation. Replace if
wear exceed the limit.
(2) Measuring piston ring gap (End clearance)
Press the piston ring onto a piston liner and measure
the piston ring gap with a gauge. Press on the ring
about 30mm from the bottom of the liner.
(3) Removing the piston rings
1) Thoroughly clean the ring grooves when removing
piston rings.
2) The side with the manufacturer’s mark should
face up.
mm
Standard Limit
First
piston ring
Groove width 2.060-2.075 2.170
Ring width 1.970-1.990 1.950
Clearance 0.070-0.105 0.200
Second
piston ring
Groove width 2.025-2.040 2.140
Ring width 1.970-1.990 1.950
Clearance 0.035-0.070 0.190
Oil ring
Groove width 4.015-4.030 4.130
Ring width 3.970-3.990 3.950
Clearance 0.025-0.060 0.180
mm
Standard Limit
First piston ring
gap
0.200-0.400 0.490
Second piston
ring gap
0.200-0.400 0.490
Oil ring gap 0.200-0.400 0.490
Width
Thickness
(Measuring side clearance)
Approx.
30 mm
Head surface
Cylinder block
Piston ring
Gap
Make the punched manufacturer's
mark face upward.
(Piston ring)