Yamaha 55DEHD, Service Manual

Page: 112 / 269

Disassembling the piston and con-
necting rod assembly
1. Remove the piston pin clips
1
with pliers,
and then remove the piston pin
2
, nee-
dle bearings
3
and washers
4
.
2. Remove the top piston ring
5
and 2nd
piston ring
6
.
Checking the bearing
1. Check the needle bearings, main bearing
and ball bearing for pitting or rumbling.
Checking the piston pin
1. Measure the piston pin outside diameter.
Replace the piston pin if out of specifica-
tion.
POWR
5-25
6885J11
Power unit
2. Remove the crankshaft assembly.
3. Remove the piston with connecting rod.
Checking the cylinder block
c C
Do not scratch the mating surfaces of the
cylinder head and cylinder block.
1. Check the cylinder sleeves. Replace the
cylinder block if cracked or damaged.
2. Remove any rust or deposits on the cool-
ing water passage walls, and check the
cooling water passage walls. Clean or
replace the cylinder block for residue.
3. Remove the carbon deposits on the
exhaust passage walls, and check the
exhaust passage walls. Replace the
cylinder block if cracked or damaged.
68850410
Piston pin outside diameter:
19.895–19.900 mm
(0.7833–0.7835 in)
69R50320
1
2
3
4
5
6
4
1
68850420
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