Valve Guide Replacement - TOHATSU BFT75A Service Manual

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CYLINDER HEAD

VALVE GUIDE REPLACEMENT

Chill the replacement new valve guides in a freezer for
about an hour.
Use a hot plate or oven to heat the cylinder evenly to
150°C (302°F). Check the temperature with a
temperature indicating stick (available at a welding
supply store) or equivalent.
• Do not use a torch to heat the cylinder head;
warpage of the cylinder head may result.
• Do not get the head hotter than 150 °C (302 °F);
excessive heat may loosen the valve seats.
Remove the heated cylinder head from the hot plate,
and support it with wooden blocks. Wear heavy gloves
to protect your hands.
Drive the valve guide out from the combustion chamber
side using a special tool.
• Be careful not to damage the cylinder head mating
surface.
TOOL:
Valve guide driver, 5.5 mm [1]
Allow the cylinder head to cool to room temperature.
Clean and inspect the valve guide bores in the cylinder
head.
Use a hot plate or oven to heat the cylinder head evenly
to 150 °C (302 °F). Check the temperature with a
temperature indicating stick or equivalent.
Install new valve guides [1] from the valve spring side of
the cylinder head.
Drive each valve guide to the specified height,
measured from the top of the valve guide to the cylinder
casting as shown.
TOOL:
Valve guide driver, 5.5 mm [2]
Valve guide installation height [3]:
IN/EX: 15.85 – 16.35 mm (0.624 – 0.644 in)
For best results, be sure the cylinder head is at room
temperature before reaming valve guides.
Coat the reamer and valve guide with cutting oil.
Rotate the reamer clockwise through the valve guide for
the full length of the reamer.
Continue to rotate the reamer clockwise while removing
it from the valve guide.
• Turn the special tool (valve guide reamer, 5.5 mm)
clockwise, never turn it counterclockwise. Continue
to turn it clockwise as you lift it from the valve guide.
TOOL:
Valve guide reamer, 5.5 mm [1]
14-40
07742-0010100
07742-0010100
07HAH-PJ7A100
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[3]
[2]
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