Yamaha FT50C - Checking the Piston Clearance; Checking the Piston Rings

POWR
Power unit
5-39
62Y5A11
2. Calculate the taper limit. Replace or
rebore the cylinder body if out of specifi-
cation.
3. Calculate the out-of-round limit. Replace
or rebore the cylinder body if out of spec-
ification.
Checking the piston clearance
1. Rebore the cylinder or replace the piston
and piston rings as a set or the cylinder
body, or both if out of specification.
Checking the piston rings
1. Check the piston ring
1
dimensions of B
and T. Replace if out of specification.
2. Level the piston ring
1
in the cylinder
with the piston crown of an inverted pis-
ton.
3. Check the piston ring end gap
d
at the
specified measuring point. Replace if out
of specification.
Taper limit = maximum of D
1
or D
2
–
minimum of D
5
or D
6
:
0.08 mm (0.003 in)
Out-of-round limit = maximum of D
1
,
D
3
, or D
5
– minimum of D
2
, D
4
, or D
6
:
0.08 mm (0.003 in)
Piston clearance:
0.04–0.06 mm (0.0016–0.0024 in)
Piston ring dimensions:
Top ring
a
:
B: 1.17–1.19 mm (0.046–0.047 in)
T: 2.39–2.41 mm (0.094–0.095 in)
Second ring
b
:
B: 1.47–1.49 mm (0.058–0.059 in)
T: 2.49–2.51 mm (0.098–0.099 in)
Oil ring
c
:
B: 2.34–2.46 mm (0.092–0.097 in)
T: 2.75 mm (0.108 in)
Piston ring end gap
d
:
Top ring:
0.15–0.30 mm (0.006–0.012 in)
Second ring:
0.30–0.50 mm (0.012–0.020 in)
Oil ring:
0.20–0.70 mm (0.008–0.028 in)
Measuring point
e
: 20 mm (0.8 in)
S62Y5780
1