Suzuki DR-Z70 Service Manual page 59

3-27 ENGINE
VALVE SEAT SERVICING
• The valve seats 1 for both the intake valve 2 and exhaust
valve 3 are machined to three different angles. The seat con-
tact surface is cut at 30°.
Seat angle
Seat width
(0.035 – 0.043 in)
Valve diameter 22.5 mm (0.89 in)
5.000 – 5.012 mm
Valve guide I.D.
(0.1969 – 0.1973 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.
NOTE:
After servicing the valve seats, be sure to check the valve clear-
ance after the cylinder head has been reinstalled.
( 2-6 and -7)
• Clean and assemble the head and valve components. Fill the
intake and exhaust ports with gasoline to check for leaks.
• If any leaks occur, inspect the valve seat and face for burrs or
other things that could prevent the valve from sealing.
Always use extreme caution when handling gasoline.
VALVE STEM END CONDITION
Inspect the valve stem end face for pitting and wear. If pitting or
wear is present, resurface the valve stem end. Make sure that
the length A is not less than 2.2 mm. If this length becomes less
than 2.2 mm, replace the valve.
Valve stem end length:
Service Limit: 2.2 mm (0.09 in)
INTAKE SIDE EXHAUST SIDE
15°, 45°
0.9 – 1.1 mm
19.0 mm (0.75 in)
←
←
←
For intake and exhaust