Cylinder Block; Cleaning; Inspection - Yamaha 50G Service Manual

POWR

INSPECTION

G61501-0*

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 cyl-
inder or re-bore 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
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 on the port
hole.
Cylinder bore size;
50, 60, 70 hp: 72.00 ~ 72.02 mm
75, 80, 90 hp: 82.00 ~ 82.02 mm
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 the cylinder or, if neces-
sary, replace the cylinder-block.
5-7
E
(2.834 ~ 2.835 in)
(3.228 ~ 3.229 in)