Checking The Piston Diameter; Checking The Cylinder Bore - Yamaha F50A Service Manual

2. Remove the crankcase bolts in the
sequence shown.
3. Remove the connecting rod bolts and the
piston assemblies.
4. Remove the crankshaft, oil seals, and
dowel pins.
5. Remove the piston pin clip 1 with pliers,
and then remove the piston.

Checking the piston diameter

1. Measure the piston outside diameter at
the specified measuring point. Replace if
out of specification.
62Y3A11
Piston diameter a:
62.95–62.96 mm (2.478–2.479 in)
Measuring point b:
5 mm (0.2 in) up from the bottom of the
piston skirt
Oversize piston diameter:
Oversize 1: +0.25 mm (0.01 in)
Oversize 2: +0.50 mm (0.02 in)

Checking the cylinder bore

1. Measure the cylinder bore (D
measuring points b, c and d, and in
direction e, which is parallel to the
crankshaft, and direction f, which is at a
right angle to the crankshaft.
Cylinder bore a:
63.00–63.01 mm (2.480–2.481 in)
Cylinder body
) a at
–D
1 6
5-56
1
2
3
4
5
6
7
8
I