Kubota WSM STV32 Workshop Manual page 121

STV32 · STV36 · STV40, WSM
Correcting Valve and Valve Seat
A Before correcting the valve and seat, check the valve
stem and the I.D. of valve guide section, and repair them
if necessary.
A After correcting the valve seat, be sure to check the valve
recessing.
1) Correcting Valve
1. Correct the valve with a valve refacer.
2) Correcting Valve Seat
1. Slightly correct the seat surface with a 1.047 rad (60 ) (intake
valve) or 0.785 rad (45 ) (exhaust valve) seat cutter (Code No.
07909-33102).
2. Resurface the seat surface with a 0.523 rad (30 ) valve seat
cutter to intake valve seat and with a 0.262 rad (15 ) valve
seat cutter to exhaust valve seat so that the width is close to
specified valve seat width (2.12 mm, 0.0835 in.).
3. After resurfacing the seat, inspect for even valve seating,
apply a thin film of compound between the valve face and
valve seat, and fit them with valve lapping tool.
4. Check the valve seating with prussian blue. The valve seating
surface should show good contact all the way around.
(a) Identical Dimensions
(b) Valve Seat Width
(c) 0.523 rad (30 ) or 0.262 rad
(15 )
(d) 0.262 rad (15 ) or 0.523 rad
(30 )
(e) 0.785 rad (45 ) or 1.047 rad
(60 )
Valve Lapping
1. Apply compound evenly to the valve lapping surface.
2. Insert the valve into the valve guide. Lap the valve onto its
seat with a valve flapper or screwdriver.
3. After lapping the valve, wash the compound away and apply
oil, then repeat valve lapping with oil.
4. Apply prussian blue to the contact surface to check the seated
rate. If it is less than 70 %, repeat valve lapping again.
A When valve lapping is performed, be sure to check the
valve recessing and adjust the valve clearance after
assembling the valve.
1-S49
ENGINE
A : Check Contact
B : Correct Seat Width
C : Check Contact
0000005444E
0000004345E
KiSC issued 04, 2006 A