Inspection Of Piston Ring Side Clearance - TOHATSU MFS25 Service Manual

27) Inspection of Piston Ring Side Clearance

1. Measure piston side clearance. Replace piston and piston
rings as a set if the clearance is over specified value.
Piston Side Clearance :
Top Ring a : 0.04 to 0.08mm ( 0.0016 to 0.0031 in )
Second Ring b : 0.03 to 0.07mm ( 0.0012 to 0.0028 in )
Oil Ring c : 0.05 to 0.15mm ( 0.0020 to 0.0059 in )
Functional Limit :
Top Ring a : 0.10 mm ( 0.0039 in )
Second Ring b : 0.09 mm ( 0.0035 in )
Oil Ring c : 0.17 mm ( 0.0067 in )
28) Inspection of Piston Rings
Push piston ring 1 into ring gauge 61.000mm ( 2.40157in )
1
parallel to top edge. Measure at the top or bottom of cylinder
bore with no wear.
2. When ring gauge is not available, use piston crown to push
piston ring 1 into to cylinder.
Measure piston ring closed gap a. Replace if the gap is
3.
over specified value.
Piston Ring Closed Gap a :
Top Ring : 0.15 to 0.30 mm ( 0.0059 to 0.018 in )
Second Ring : 0.35 to 0.50 mm ( 0.0138 to 0.0197 in )
Oil Ring : 0.20 to 0.70 mm ( 0.0079 to 0.0276 in )
Functional Limit :
Top Ring : 0.50 mm ( 0.0197 in )
Second Ring : 0.70 mm ( 0.0276 in )
Replace oil ring when top ring or second ring is
replaced.
25/30 2006
1
a
a
b
c
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