Cub-cadet Yanmar 3TNV72 User Manual download pdf (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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Cub-cadet Yanmar 3TNV72 User Manual Page 133

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