ENGINE
6-66
TNV DI Service Manual
Measuring and Adjusting Valve Clearance
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 the radiator. The firing
order is 1-3-2 for 3-cylinder engines and
1-3-4-2 for 4-cylinder engines.
• 3-cylinder engines fire every 240° of crankshaft
rotation.
• 4-cylinder engines fire every 180° of crankshaft
rotation.
• 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 cylinder
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. Make adjustment for
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, other cylinders can also
be checked as indicated in the chart below.
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
4-Cylinder Engines
Cylinder No.
1
2
3
Valve
Intake
Exhaust
Intake
Exhaust
Intake
Exhaust
No. 1 Cylinder at TDC
Compression
•
•
•
•
No. 1 Cylinder at TDC Exhaust
•
•
Cylinder No.
1
2
3
4
Valve
Intake
Exhaust
Intake
Exhaust
Intake
Exhaust
Intake
Exhaust
No. 1 Cylinder at TDC
Compression
•
•
•
•
No. 4 Cylinder at TDC
Compression
•
•
•
•
TNV_DI_SM_A4.book 66 ページ 2007年12月6日 木曜日 午前9時23分