Valve Seat Reconditioning - TOHATSU BFT75A Service Manual

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Thoroughly clean the cylinder head to remove any
cutting residue.
Check the valve guide bore; it should be straight, round
and centered in the valve guide. insert the valve and
check operation. If the valve does not operate
smoothly, the guide may have been bent during
installation.
Replace the valve guide if it is bent or damaged.
Check the Valve Stem-to-Valve Guide Clearance (page
14-33).

VALVE SEAT RECONDITIONING

Thoroughly clean the combustion chambers and valve
seats to remove carbon deposits.
Apply a light coat of Prussian Blue compound or
erasable felt-tipped marker ink to the valve faces [1].
Insert the valves, and then lift them and snap them
closed against their seats several times.
Be sure the valve does not rotate on the seat.
The transferred marking compound will show any area
of the seat that is not concentric.
Using the 45° cutter, remove enough material to
produce a smooth and concentric seat. Follow the valve
seat cutter manufacturer's instructions.
Turn the cutter clockwise, never counterclockwise.
Continue to turn the cutter as you lift it from the valve
seat.
TOOLS (commercially available)
Valve seat cutter, #123 32°
Valve seat cutter, #122 45°
Valve seat cutter, # 111 60°
Solid pilot bar, 5.5 mm
Solid pilot bar, 5.52 mm
T-wrench, #505
Accessory package, #246
[1]
NWY-CU123
NWY-CU608
NWY-CU270
NWY-140-5.5
NWY-100-5.52
NWY-TW-505
NWY-KACC246
CYLINDER HEAD
CORRECT
INCORRECT
14-41