Inspection And Repair; Cylinder Head; Valve Seat - Yamaha TTR250L Service Manual

INSPECTION AND REPAIR

NB243001
INSPECTION AND REPAIR

CYLINDER HEAD

1.Eliminate:
Carbon deposit
(from combustion chamber)
Use rounded scraper 1.
NOTE:
Do not use a sharp instrument and avoid
damaging or scratching:
Spark plug thread

Valve seat

2.Inspect:
Cylinder head
Scratches/damage → Replace.
3.Measure:
Warpage
Out of specification → Resurface.
Cylinder head warpage:
Less than 0.03 mm (0.0012 in)
4.Resurface:
Cylinder head
*********************************
Resurfacement steps:
Place a 400 ~ 600 grit wet sandpaper on
the surface plate, and resurface the head
using a figure-eight sanding pattern.
NOTE:
Rotate the head several times to avoid
removing too much material from one side.
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NB243002
VALVE SEAT
1.Eliminate:
Carbon deposit
(from valve face and valve seat)
2.Inspect:
Valve seat
Pitting/wear → Reface the valve seat.
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