Cylinder Block; Cleaning; Inspection - Yamaha 25J Service Manual

POWR

INSPECTION

G61500-0

CYLINDER BLOCK

Cleaning

1. Using a gasket-scraper, remove all
traces of gasket material from the cylin-
der-block surface.
2. Using a soft brush and solvent, clean
the cylinder-block.
Inspection
1. Visually inspect the cylinder sleeves for
cracks and scratches.
If cracks are found, replace the cylinder
block. If scratches are found, check the
degree of out-of-round, and then hone
the cylinder or rebore it if necessary.
2. Using a cylinder-gauge, measure the
cylinder bore at three positions in the
thrust and axial directions.
1 Axial direction
2 Thrust direction
Cylinder bore size:
59.50 ~ 59.52 mm
(2.3425 ~ 2.3433 in)
Taper limit:
0.08 mm (0.003 in)
Out of round limit:
0.05 mm (0.002 in)
If diameter is greater than the limit,
hone or rebore all cylinders or, if neces-
sary, replace the cylinder-block
A: 10 mm (0.4 in) below the cylinder top
B: 5 mm (0.2 in) above the exhaust port
C: 5 mm (0.2 in) below the scavenging port
NOTE:
Do not place the cylinder-gauge in the port
hole.
5-5
E