Service manual
Table Of Contents
- Inroduction
- Yamaha Motor Corporation, USA YZ/WR Motorcycle Limited Warranty
- How to use this Manual
- Index
- Contents
- Chapter 1 General Information
- Chapter 2 Specifications
- Chapter 3 Regular Inspection and Adjustments
- Chapter 4 Engine
- Seat, Fuel Tank and Side Covers
- Exhaust Pipe and Silencer
- Radiator
- Carburetor and Reed Valve
- Cylinder Head, Cylinder and Piston
- Clutch and Primary Driven Gear
- Kick Axle, Shift Shaft and Primary Drive Gear
- YPVS Govenor
- Water Pump
- CDI Magneto
- Engine Removal
- Crankcase and Crankshaft
- Transmission, Shift Cam and Shift Fork
- Chapter 5 Chassis
- Chapter 6 Electrical
- Chapter 7 Tuning
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4-21
ENG
CYLINDER HEAD, CYLINDER AND PISTON
EC474302
Piston
1. Eliminate:
9
Carbon deposits
From the piston crown a and ring groove
b.
2. Inspect:
9
Piston wall
Score marks → Repair or replace.
3. Measure:
9
Piston skirt diameter
Use micrometer 1.
Measure the specific distance a from the
bottom edge.
Out of specification → Replace.
2. Inspect:
9
Cylinder inner surface
Score marks → Repair or replace.
Use #400~600 grit wet sandpaper.
cC
Do not rebore the cylinder.
3. Measure:
9
Cylinder bore “C”
Use cylinder gauge 1.
Out of limit → Replace.
NOTE:
Measure the cylinder bore “C” in parallel (A, B,
C) to and at right angles to the crankshaft (a, b).
Then, find the average of the measurements.
17.5 mm 53.957~53.972 mm
(0.69 in) (2.1243~2.1249 in)
Standard Wear limit
Cylinder 54.000~54.014mm 54.1 mm
bore “C” (2.1260~2.1265 in) (2.130 in)
Taper “T” —
0.05 mm
(0.0020 in)
C=Maximum Aa~Cb
T=(Maximum Aa, or Ab) —
(Maximum Ba, or Bb)
Distance
a
Piston dia.
1C3-28199-10 110 04.5.17, 9:22:10 PM