Exmark 127-9041 Service Manual page 33

Exhaust Valve Guide Reaming
For best results, be sure the cylinder head is at
room temperature before reaming the exhaust valve guide.
1. Coat the reamer and valve guide with cutting oil.
2. Rotate the reamer clockwise through the valve
guide the full length of the reamer.
3. Continue to rotate the reamer clockwise while
removing it from the valve guide.
4. Thoroughly clean the cylinder head to remove
any cutting residue.
5. 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.
6. Check the valve stem-to-guide clearance
Valve Seat Reconditioning
1. Thoroughly clean the combustion chambers
and valve seats to remove carbon deposits.
2. Apply a light coat of Prussian Blue or erasable
felt-tipped marker ink to the valve faces.
3. Insert the valve, 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.
4. Using a 45°cutter, remove enough material to
produce a smooth and concentric seat. Follow the
valve seat cutter manufacture's instructions.
Turn the cutter clockwise, never counterclockwise.
Continue to turn the cutter as you lift it from the
valve seat.
5. Using the 30°~32° and 60° cutter to narrow
and adjust the valve seat so that it contacts the
middle of the valve face. The 30°~32° cutter removes
material from the top edge. The 60° cutter removes
material from the bottom edge. Bu sure that the width
of the finished valve seat is within specification.
4－14
Maintenance
VALVE
REAMER 0.259"
CONTACT TOO HIGH
CONTACT TOO LOW
GUIDE