Measuring And Adjusting Valve Clearance - Yanmar 2TNV70 Service Manual

ENGINE
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.
3-Cylinder Engines
Cylinder No.
Valve
No. 1 Cylinder at TDC
Compression
No. 1 Cylinder at TDC Exhaust
1. Remove the intake manifold / valve cover. See
Removal of Intake Manifold / Valve Cover on
page 6-20.
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.)
6-32
• If there is no valve clearance, and the piston is at
• If adjusting each cylinder individually, the cylinder
• To decrease the number of rotations required to
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).
1
Intake Exhaust
• •
TDC of the compression stroke, extreme wear or
damage to the cylinder head or valves may be
possible.
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.
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.
2
Intake Exhaust
•
•
TNV IDI Service Manual
Cylinder Head
3
Intake Exhaust
•
•