Yamaha YZ450F(Y) Instrukcja Obsługi Pobierz pdf (Strona 105)

4-24

CYLINDER AND PISTON

REMOVING THE PISTON AND

PISTON RING

1. Remove:

• Piston pin clip "1"

• Piston pin "2"

• Piston "3"

• Put identification marks on each

piston head for reference during re-

installation.

• Before removing each piston pin,

deburr the clip groove and pin hole

area. If the piston pin groove is de-

burred and the piston pin is still dif-

ficult to remove, use the piston pin

puller set "4".

Do not use a hammer to drive the

piston pin out.

2. Remove:

• Piston ring "1"

Spread the end gaps apart while at

the same time lifting the piston ring

over the top of the piston crown, as

shown in the illustration.

CHECKING THE CYLINDER AND

PISTON

1. Inspect:

• Cylinder and piston walls

Vertical scratches → Replace cyl-

inder and piston.

2. Measure:

• Piston-to-cylinder clearance

Measurement steps:

a. Measure the cylinder bore "C"

with a cylinder bore gauge.

Measure the cylinder bore "C" in par-

allel to and at right angles to the

crankshaft. Then, find the average of

the measurements.

b. If out of specification, replace the

cylinder, and replace the piston

and piston rings as set.

c. Measure the piston skirt diameter

"P" with a micrometer.

a. 9 mm (0.35 in) from the piston

bottom edge.

d. If out of specification, replace the

piston and piston rings as a set.

e. Calculate the piston-to-cylinder

clearance with following formula:

f. If out of specification, replace the

cylinder, and replace the piston

and piston rings as set.

CHECKING THE PISTON RING

1. Measure:

• Ring side clearance

Use a feeler gauge "1".

Out of specification → Replace

the piston and rings as a set.

Clean carbon from the piston ring

grooves and rings before measuring

the side clearance.

Piston pin puller set:

YU-1304/90890-01304

Cylinder

bore "C"

97.00–97.01 mm

(3.8189–3.8193 in)

Taper limit

"T"

0.05 mm (0.002 in)

Out of

round "R"

0.05 mm (0.002 in)

"C" = Maximum D

"T" = (Maximum D

1

or D

2

) - (Max-

imum D

5

or D

6

)

"R" = (Maximum D

1

, D

3

or D

5

) -

(Minimum D

2

, D

4

or D

6

)

Piston size "P"

Standard

96.965–96.980 mm

(3.8175–3.8181 in)

Piston-to-cylinder clearance =

Cylinder bore "C" - Piston skirt

diameter "P"

Piston-to-cylinder clear-

ance:

0.020–0.045 mm

(0.0008–0.0018 in)

<Limit>:0.1 mm (0.004

in)

Side clearance:

Standard <Limit>

Top

ring

0.015–0.065

mm

(0.0006–0.0

026 in)

0.12 mm

(0.005 in)

2nd

ring

0.020–0.060

mm

(0.0008–0.0

024 in)

0.12 mm

(0.005 in)

1 2 ... 100 101 102 103 104 105 106 107 108 109 110 ... 229 230

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