Cub Cadet Yanmar 3TNV72 - Manual (Page 133)

ENGINE
6-34 TNV IDI Service Manual
Cylinder Head
Measuring and Adjusting Valve
Clearance
Measure and adjust while the engine is cold.
Notes:
• The No. 1 piston position is on the flywheel end
of the engine, opposite end of the radiator. The
firing order is 1-3-2 for 3-cylinder engines and
1-2 for 2-cylinder engines.
• 3-cylinder engines fire every 240° of crankshaft
rotation.
• 2-cylinder engines are an uneven firing engine.
No. 2 cylinder fires 180° after No. 1. The
crankshaft then rotates 540° before No. 1
cylinder fires again.
• Valve clearance of both the intake and exhaust
valves can be checked with the piston for that
cylinder at top dead center (TDC) of the
compression stroke. When a piston is at TDC
of the compression stroke, both rocker arms
will be loose and the cylinder TDC mark on the
flywheel will be visible in the timing port of the
flywheel housing.
• If there is no valve clearance, and the piston is
at TDC of the compression stroke, extreme
wear or damage to the cylinder head or valves
may be possible.
• If adjusting each cylinder individually, the
cylinder to be adjusted first does not have to be
the No. 1 cylinder. Select and adjust the
cylinder where the piston is nearest to the top
dead center after turning. Adjust the remaining
cylinders in the order of firing by turning the
crankshaft each time.
• To decrease the number of rotations required
to check all cylinders of a 3-cylinder engine,
other cylinders can also be checked as
indicated in the chart below. 2-cylinder engines
must have each cylinder adjusted when the
piston is at TDC.
Example: On a 3-cylinder engine, with the No. 1
piston at TDC on the compression stroke (both
valves closed), the valves indicated on the top line
of the chart can be adjusted without rotating the
crankshaft. To adjust the remaining two valves,
rotate the crankshaft until the No. 1 piston is at TDC
on the exhaust stroke (exhaust valve only open).
3-Cylinder Engines
1. Remove the intake manifold / valve cover. See
Removal of Intake Manifold / Valve Cover on
page 6-22.
2. Rotate the crankshaft clockwise as seen from
the coolant pump end, to bring No. 1 piston to
TDC of the compression stroke while watching
the rocker arm motion and timing grid on the
flywheel. (Position so both the intake and
exhaust valves are closed.)
3. Insert a feeler gauge (Figure 6-35, (1))
between rocker arm and valve cap and record
the measured valve clearance. (Use the data
for estimating wear.)
Cylinder No. 1 2 3
Valve Intake Exhaust Intake Exhaust Intake Exhaust
No. 1 Cylinder at TDC
Compression
• • • •
No. 1 Cylinder at TDC Exhaust • •
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