Piston Clearance - Yamaha V star 1100 Owner's Manual

126
sary, clean the holes and blow them out with com-
pressed air.
5. Check the piston skirt (B, Figure 122) for gall-
ing and abrasion, which may have been caused by
piston seizure. If a piston shows signs of partial sei-
zure (bits of aluminum build-up on the piston skirt),
replace the piston to reduce the possibility of engine
noise and further piston seizure. When replacing
the piston, lightly hone the cylinder with a
bottlebrush hone.
NOTE
If the piston skirt is worn or scuffed
unevenly from side to side, the con
necting rod may be bent or twisted.
6. Check the circlip groove on each side of the pis-
ton for wear or other damage. Install a new circlip
into each piston circlip groove and try to move the
clip from side to side. If the circlip has any side play,
the groove is worn and the piston must be replaced.
7. Measure the outside diameter of the piston
across the skirt at right angles to the piston pin.
Measure the piston at a point 5 mm (0.20 in.) up
from the bottom of the piston skirt (Figure 125). If
the piston diameter is out of specification, replace
the piston and rings as a set. When installing the
new piston, lightly hone the cylinder with a
bottlebrush hone.
8. Measure the piston-to-cylinder clearance as de-
scribed in Piston Clearance in this section. If clear-
ance is out of specification (Table 2), replace the
cylinder, piston and rings as a set. Oversized pistons
are not available.

Piston Clearance

1. Make sure the pistons and cylinder walls are
clean and dry.
2. Measure the cylinder bore with a cylinder bore
gauge (Figure 115) at a point 40 mm (1.57 in.) be-
low the top of the cylinder block. Measure the cylin-
der bore in two axes: in-line with the piston pin and
90° to the pin. Calculate the average of the two mea-
surements. This average is the cylinder bore
diameter.
3. Measure the outside diameter of the piston
across the skirt at right angles to the piston pin.
Measure the piston at a point 5 mm (0.20 in.) up
from the bottom of the piston skirt (Figure 125).
125
Specified
distance
90°
126
127
4. Piston-to-cylinder clearance is the difference be-
tween the piston outside diameter and the cylinder
bore diameter. Subtract the outside diameter of the
piston from the cylinder bore diameter calculated in
Step 2. If the piston-to-cylinder clearance is out of
specification (Table 2), replace the cylinder, piston
and rings as a set. Oversized pistons are not available.
CHAPTER FOUR