Snowmobile Yamaha Phazer PZ50W, PZ50GTW, PZ50FXW, PZ50MW, PZ50VTW, PZ50MPW. Instruction - part 56

5-61

ENG

CRANKCASE

REMOVAL

1. Remove:

• Crankcase bolts

NOTE:

• Loosen the bolts in decreasing numerical order of

the embossed numbers on the crankcase.

• Loosen each bolt 1/4 of a turn at a time. After all

of the bolts are fully loosened, remove them.

È Cylinder head side
É Oil pan side

17

18

19

È

3

4

10

8

7

9

11

1
2

5

6

13

12

14

15

É

2. Remove:

• Lower crankcase

CAUTION:

Tap on one side of the crankcase with a soft-
face hammer. Tap only on reinforced portions
of the crankcase, not on the crankcase mating
surfaces. Work slowly and carefully and make
sure that the crankcase halves separate evenly.

3. Remove:

• Dowel pins
• Crankshaft journal bearing

NOTE:

Identify the position of each crankshaft journal
lower bearing so that it can be reinstalled in its orig-
inal place.

4. Remove:

• Connecting rod cap 1 
• Big end bearing

NOTE:

Identify the position of each big end bearing so that
it can be reinstalled in its original place.

1

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CRANKCASE

5. Remove:

• Piston pin clips 1 
• Piston pin 2 
• Piston 3 
• Connecting rod 4 

CAUTION:

Do not use a hammer to drive the piston pin
out.

NOTE:

• For reference during installation, put identification

marks on the piston crown.

• Before removing the piston pin, deburr the piston

pin clip’s groove and the piston’s pin bore area. If
both areas are deburred and the piston pin is still
difficult to remove, remove it with the piston pin
puller 5.

Piston pin puller:

90890-01304, YU-01304

4

3

2

1

6. Remove:

• Top ring
• 2nd ring
• Oil ring

NOTE:

When removing a piston ring, open the end gap
with your fingers and lift the other side of the ring
over the piston crown.

7. Remove:

• Crankshaft
• Crankshaft journal bearing

NOTE:

Identify the position of each crankshaft journal
upper bearing so that it can be reinstalled in its orig-
inal place.

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ENG

CRANKCASE

INSPECTION

1. Inspect:

• 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

Measurement steps:
1st step:

• Measure cylinder bore “C” with the cylinder bore

gauge 1.

NOTE:

Measure cylinder bore “C” by taking side-to-side
and front-to-back measurements of the cylinder.
Then, find the average of the measurements.

• If out of specification, replace the cylinder, and

the piston and piston rings as a set.

2nd step:

• Measure piston skirt diameter “P” with the

micrometer.

a 11.0 mm (0.43 in) from the bottom edge of the piston.

• If out of specification, replace the piston and

piston rings as a set.

Cylinder bore “C”

77.000 ~ 77.010 mm 

(3.0315 ~ 3.0319 in)

Taper limit “T”

0.050 mm (0.0020 in)

Out of round “R”

0.050 mm (0.0020 in)

“C” = maximum of D

1

 ~ D

6

“T” = maximum of D

1

 or D

2

 – maximum of D

5

 

or D

6

“R” = maximum of D

1

, D

3

 or D

5

 – maximum of 

D

2

, D

4

 or D

6

Piston size (standard) (P):

76.955 ~ 76.970 mm
(3.0297 ~ 3.0303 in)

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CRANKCASE

3rd step:

• Calculate the piston-to-cylinder clearance with

the following formula.

Piston-to-cylinder clearance = 

Cylinder bore “C” –
Piston skirt diameter “P”

• If out of specification, replace the cylinder, and

the piston and piston rings as a set.

Piston-to-cylinder clearance:

0.030 ~ 0.055 mm
(0.0012 ~ 0.0022 in)
<Limit>: 0.120 mm (0.0047 in)

3. Measure:

• Piston ring side clearance

Use the thickness gauge 1.
Out of specification 

→ Replace the piston and

piston rings as a set.

NOTE:

Eliminate the carbon deposits from the piston ring
grooves and rings before measuring the side clear-
ance.

Piston rings side clearance:

Top ring:

0.030 ~ 0.065 mm
(0.0012 ~ 0.0026 in)

2nd ring:

0.020 ~ 0.055 mm
(0.0008 ~ 0.0022 in)

4. Install:

• Piston ring

(into the cylinder)

NOTE:

Level the piston ring in the cylinder with the piston
crown.

a 5.0 mm (0.20 in)