Checking The Cylinder And Piston - Yamaha YJ50RAP Service Manual

CYLINDER HEAD, CYLINDER AND PISTON
1
2
a. Place a straightedge 1 and a thickness
gauge 2 across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylin-
der head as follows.
d. Place a 400 ~ 600 grit wet sandpaper on
the surface plate and resurface the cylinder
head using a figure-eight sanding pattern.
NOTE:
@
To ensure an even surface, rotate the cylinder
head several times.
EAS00255

CHECKING THE CYLINDER AND PISTON

1. Check:
• piston wall
• cylinder wall
Vertical scratches → Rebore or replace the
cylinder, and replace the piston and piston
rings as a set.
2. Measure:
• piston-to-cylinder clearance
a. Measure cylinder bore "C" with the cylinder
bore gauge.
NOTE:
@
Measure cylinder bore "C" by taking side-to-
side and front-to-back measurements of the
cylinder. Then, find the average of the mea-
surements.
Cylinder bore "C"
Max. taper "T"
Out-of-round "R"
"C" = maximum of D
"T" = maximum of D
D or D
5 6
"R" = maximum of D
mum of D , D
2 4
5 - 7
ENG
39.993 ~ 40.012 mm
(1.5745 ~ 1.5753 in)
0.05 mm (0.002 in)
0.05 mm (0.002 in)
~ D
1 6
or D – maximum of
1 2
, D or D – mini-
1 3 5
or D
6