Yamaha TTR90(M) Owner's Service Manual page 192

CYLINDER AND PISTON
"C" = Maximum D
"T" = (Maximum D
"R" = (Maximum D
If out of specification, replace the cylinder,
and replace the piston and piston rings as
set.
2nd step:
Measure the piston skirt diameter "P" with
a micrometer.
a 4 mm (0.16 in) from the piston bottom edge.
Standard
If out of specification, replace the piston
and piston rings as a set.
3rd step:
Calculate the piston-to-cylinder clearance
with following formula:
Piston-to-cylinder clearance =
Cylinder bore "C" –
Piston skirt diameter "P"
Piston-to-cylinder clearance:
0.025 ~ 0.045 mm
(0.0010 ~ 0.0018 in)
<Limit>: 0.15 mm (0.0059 in)
If out of specification, replace the cylinder,
and replace the piston and piston rings as
set.
4 - 23
ENG
or D )
1 2
– (Maximum D or D
5
, D or D )
1 3 5
– (Minimum D , D or D
2 4
Piston size P
46.960 ~ 46.975 mm
(1.8488 ~ 1.8494 in)
)
6
)
6