HYOSUNG RX 125 Service Manual page 46

1. Insert with a slight rotation, the solid pilot that
gives a snug fit. The shoulder on the pilot
should be about 10㎜ from the valve guide.
2. Using the 45�cutter, descale and cleanup the
seat with one or two turns.
3. Inspect the seat by the previous seat width
measurement procedure. If the seat is pitted or
burned, additional seat conditioning with the
45�cutter is required.
CAUTION
Cut the minimum amount necessary from the
seat to prevent the possibility of the valve stem
becoming too close to the rocker arm for correct
valve contact angle.
If the contact area is too low or too narrow, use the
45�cutter to raise and widen the contact area. If
the contact area is too high or too wide, use the
15�cutter to lower and narrow the contact area.
4. After the desired seat position and width is
achieved, use be 45�cutter very lightly to clean
up any burrs caused by the previous cutting
operations. DO NOT use lapping compound
after the final cut is made. The finished valve
seat should have a velvety smooth finish and
not a highly polished or shiny finish. This will
provide a soft surface for the final seating of the
valve which will occur during the first few sec
onds of engine operation.
5. Clean and assemble the head and valve com-
ponents. 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.
WARNING
Always use extreme caution when handling
gasoline.
CAUTION
Be sure to adjust the valve clearance after
reassembling the engine.
ENGINE 3-16