Checking The Valve Seats - Yamaha WR250R Service Manual
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Also See for WR250R:
- Owner's manual (100 pages) ,
- Owner's manual (98 pages) ,
- Owner's manual (112 pages)
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NOTE:
After replacing the valve guide, reface the valve
seat.
Valve guide remover (ø4.5)
90890-04116
YM-04116
Valve guide installer (ø4.5)
90890-04117
YM-04117
Valve guide reamer (ø4.5)
90890-04118
YM-04118
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3. Eliminate:
Carbon deposits
G
(from the valve face and valve seat)
4. Check:
Valve face
G
Pitting/wear → Grind the valve face.
Valve stem end
G
Mushroom shape or diameter larger than the
body of the valve stem → Replace the valve.
5. Measure:
Valve margin thickness "a"
G
Out of specification → Replace the valve.
Valve margin thickness
Valve margin thickness D (intake)
1.15–1.45 mm (0.0453–0.0571 in)
Limit
1.00 mm (0.0394 in)
Valve margin thickness D (ex-
haust)
0.85–1.15 mm (0.0335–0.0453 in)
Limit
0.70 mm (0.0276 in)
VALVES AND VALVE SPRINGS
6. Measure:
Valve stem runout
G
Out of specification → Replace the valve.
NOTE:
When installing a new valve, always replace
G
the valve guide.
If the valve is removed or replaced, always re-
G
place the oil seal.
Valve stem runout
0.010 mm (0.0004 in)
EAS24300
CHECKING THE VALVE SEATS
The following procedure applies to all of the
valves and valve seats.
1. Eliminate:
Carbon deposits
G
(from the valve face and valve seat)
2. Check:
Valve seat
G
Pitting/wear → Replace the cylinder head.
3. Measure:
Valve seat width "a"
G
Out of specification → Replace the cylinder
head.
Valve seat width
Valve seat width C (intake)
0.90–1.10 mm (0.0354–0.0433 in)
Valve seat width C (exhaust)
0.90–1.10 mm (0.0354–0.0433 in)
5-20
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