Toro 500 EFI Service Manual page 49

Installing Piston Rings
1. Install ring expander (4) in the bottom groove of the
piston; then install the thin oil rings (3) over the
expander making sure the expander ends do not
overlap. Stagger the end gaps of the upper and lower
thin oil rings according to the illustration.

NOTE: Note the direction of the exhaust side of the
piston (5) for correct ring end gap orientation.
2. Install the compression rings (1 and 2) so the letter(s)
on the top surface of each ring faces the dome of the
piston. Rotate the rings until the ring end gaps are on
directly opposite sides of the piston according to the
illustration.

NOTE: The chrome (silver) ring should be installed
in the top position.
CAUTION
Incorrect installation of the piston rings will result in
engine damage.
CYLINDER /CYLINDER HEAD
ASSEMBLY

NOTE: If the cylinder/cylinder head assembly can-
not be trued, they must be replaced.
Cleaning/Inspecting Cylinder Head
The cylinder head studs must be removed for this pro-
cedure.
1. Using a non-metallic carbon removal tool, remove
any carbon buildup from the combustion chamber
being careful not to nick, scrape, or damage the com-
bustion chamber or the sealing surface.
2. Inspect the spark plug hole for any damaged threads.
Repair damaged threads using a "heli-coil" insert.
3. Place the cylinder head on the surface plate covered
with #400 grit wet-or-dry sandpaper. Using light
pressure, move the cylinder head in a figure eight
motion. Inspect the sealing surface for any indication
of high spots. A high spot can be noted by a bright
metallic finish. Correct any high spots before assem-
bly by continuing to move the cylinder head in a fig-
ure eight motion until a uniform bright metallic
finish is attained.
ATV-1085B
Water or parts-cleaning solvent must be used in con-
junction with the wet-or-dry sandpaper or damage to
the sealing surface may result.
Measuring Cylinder Head Distortion
1. Remove any carbon buildup in the combustion
chamber.
2. Lay a straightedge across the cylinder head; then
using a feeler gauge, check the distortion factor
between the head and the straightedge.
3. Maximum distortion must not exceed specifications.
MD1343A
Cleaning/Inspecting Cylinder
1. Wash the cylinder in parts-cleaning solvent.
2. Inspect the cylinder for pitting, scoring, scuffing,
warpage, and corrosion. If marks are found, repair
the surface using a cylinder hone (see Honing Cylin-
der in this sub-section).
CAUTION
CAUTION
CC141D
47