Toro GTS 120 Service Manual page 25

Exhaust Port
Cylinder bore
The cylinder bore is checked by measuring the
cylinder liner at a total of six places using a
cylinder gauge. Two measurements, apart,
must be taken at the approximate A, 6 and C
elevations as shown. Readings larger than the
listed specifications indicate an excessively
worn bore and the cylinder block must be re-
placed. The cylinder liner is not a serviceable
part of the engine.
Intake Port
Third Port
Cylinder Bore Diameter
58.000-58.115mm
(2.284-2.288 in)
Piston to Cylinder Clearance
The piston is cam ground into a slightly oval
shape to compensate for heat distortion during
operation. The piston diameter is measured per-
pendicular to the wrist pin hole at a point above
2.5mm (1 in)
the piston skirt as indicated. Subtract the piston
measurement from the largest cylinder reading
to determine the clearance. Replace the cylinder
block or the piston if the clearance is excessive.
Piston Diameter = .1mm (.004
in) or less
Wrist Pin
-
Wrist Pin Hole
The wrist pin and wrist pin hole must be properly
fitted for efficient engine performance. Measure
the wrist pin and check the diameter of the piston
holes to be no more than the oversize dimension
indicated.
Largest Cylinder Diameter minus
Wrist
Pin
Diameter
11.955-12.005mm (.472-.473 in)
Maximum Hole Diameter
.050mm (.002 in) Oversize
/ - -
Piston Ring End Gap
Use the piston to position the piston ring at the
most worn area of the cylinder liner. (The most
wear will occur where the rings normally travel
during operation or the area of largest diameter
as measured earlier.) Use a feeler gauge to
check the gap between the ends of the piston
ring.
max gap
Piston Ring Side Clearance
De-carbon the piston rings and grooves. Hold the
piston rings into the grooves and use a feeler
gauge between the bottom of each ring and
groove to determine clearance.
IMPORTANT: The letter "R" must face the top of
the piston.