Toro 500 EFI Service Manual page 84

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NOTE: The valve seals must be replaced.
3. Remove the valve springs; then invert the cylinder head
and remove the valves.
Measuring Valve Guide (Bore)
1. Insert a snap gauge 1/2 way down into each valve
guide bore; then remove the gauge and measure it
with a micrometer.
2. Acceptable inside diameter range must be within
specifications.
3. If a valve guide is out of tolerance, it must be
replaced.
Servicing Valves/Valve Guides/Valve
Seats
If valves, valve guides, or valve seats require servicing or
replacement, Toro recommends that the components be
taken to a qualified machine shop for servicing.
CAUTION
If valves are discolored or pitted or if the seating sur-
face is worn, the valve must be replaced. Do not attempt
to grind the valves or severe engine damage may occur.
Installing Valves
1. Apply grease to the inside surface of the valve seals;
then place a lower spring seat and valve guide seal
over each valve guide.
2. Insert each valve into its original location.
3. Install the valve springs with the painted end of the
spring facing away from the cylinder head.
82
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NOTE: If the paint is not visible, install the ends of
the springs with the closest wound coils toward the
head.
CC136D
4. Place a spring retainer over the valve springs; then
using the valve spring compressor, compress the
valve springs and install the valve cotters.
PISTON ASSEMBLY

NOTE: Whenever a piston, rings, or pin are out of
tolerance, they must be replaced.
Inspecting Piston
1. Inspect the piston for cracks in the piston pin, dome,
and skirt areas.
2. Inspect the piston for seizure marks or scuffing.
Repair with #400 grit wet-or-dry sandpaper and
water or honing oil.

NOTE: If scuffing or seizure marks are too deep to
correct with the sandpaper, replace the piston.
3. Inspect the perimeter of each piston for signs of
excessive "blowby." Excessive "blowby" indicates
worn piston rings or an out-of-round cylinder.
Removing Piston Rings
1. Starting with the top ring, slide one end of the ring
out of the ring-groove.
CC144D
ATV-1011A
CC132D