Inspection Of Valve Seat - TOHATSU MFS25 Service Manual

Power Unit

12) Inspection of Valve Seat

1. Remove carbon built up on the valve.
2. Apply thin coat of red lead on the valve seat.
3. Use valve lapper (commercially available item) as shown to
push valve onto valve seat lightly.
4. Measure width of area where valve face contacted with valve
seat a that can be identified with red lead adhered to valve
face. Correct valve seat if contact area is above or below the
center or contact area of valve seat is over specified limit.
Valve Sear Contact Width a : Standard Value
Intake/Exhaust Side : 1.0 mm ( 0.04 in )
Functional Limit :
Intake/Exhaust Side : 2.0 mm ( 0.08 in )
5-34
a
25/30 2006