Valve Seat Correction - Takeuchi TB 175 Handbuch

4. Disassembly, inspection and reassembly of engines

4.2.6 Valve seat correction

[NOTICE]
Always check the oil clearance between the valve and valve guide before correcting the valve seat. If it
exceeds the limit, replace the valve or valve guide first to make the clearance satisfy the standard. After
correction, wash the valve and the cylinder head sufficiently with diesel oil to remove all grinding powder or
compound.
1)If the seat surface is slightly roughened: perform
[A] and [B] below.
[A]: Lap the valve and seat with a mixture of valve
compound and engine oil.
[B]: Lap with engine oil only.
2)If the seat is heavily roughened but the width is
almost normal, correct with a seat grinder or seat
cutter first. Then perform lapping [A] and [B].
Seat cutter angle
3)If the seat is heavily roughened and the width is
much enlarged, grind the seat inner surface with a
seat grinder whose center angle is 40°, then grind
the seat outer surface with a grinder whose center
angle is 150° to make the seat width match the stan-
dard. Then perform seat correction as described in
2), and then carry out lapping [A] and [B].
Grinding wheel angle
intake Exhaust
120 90
θ 1 θ 2
40 150
Seat angle
150
Cylinder head correction angle
Grinder
80
40
Seat width
Seat cutter
Grindstone
Seat grinder