Suzuki TU250X, Service Manual

Page: 78 / 370

ENGINE 3-31
VALVE SEAT WIDTH INSPECTION
Visually check for valve seat width on each valve face.
If the valve face has worn abnormally, replace the valve.
Coat the valve seat with a red lead (Prussian Blue) and set the
valve in place. Rotate the valve with light pressure. Check that
the transferred red lead (blue) on the valve face is uniform all
around and in center of the valve face.
If the seat width
W
measured exceeds the standard value, or
seat width is not uniform, reface the seat using the seat cutter.

Valve seat width
W
Standard (IN. & EX.): 0.9 – 1.1 mm (0.035 – 0.043 in)

09916-10911: Valve lapper set
VALVE SEAT SERVICING
• The valve seats
1
for both the intake valve and exhaust valve
are machined to two different angles. The seat contact sur-
face is cut at 45°.

NOTE:
After servicing the valve seats, be sure to check the valve clear-
ance after the cylinder head has been reinstalled. (

2-5)
INTAKE EXHAUST
Valve seat angles 30°, 45° 15°, 45°
Valve seat width
0.9 – 1.1 mm
(0.035 – 0.043 in)
←
Valve diameter 34 mm (1.3 in) 29 mm (1.1 in)
Valve guide I.D.
5.500 – 5.512 mm
(0.2165 – 0.2170 in)
←
* The valve seat contact area must be inspected after
each cut.
* Do not use lapping compound after the final cut is
made. The finished valve seat should have a velvety
smooth finish but not a highly polished or shiny fin-
ish. This will provide a soft surface for the final seat-
ing of the valve which will occur during the first few
seconds of engine operation.
45˚
15˚
45˚
30˚
IN. EX.