Lister Petter TR1, Workshop Manual

Page: 25 / 121

page 25
02.18 VALVE CLEARANCE
The valve clearance must be measured and
adjusted when the engine is cold. It is important that
the clearances are maintained correct to prevent
serious damage to the valve gear. With new engines,
or engines which have just been overhauled, the valve
gear beds down rapidly during the first 500 hours
running and it is essential that the clearance is
checked every 25 hours until it is found that the
clearances remain constant. The periods between
adjustments may then be increased to 1000 hours.
Adjusting the Valve Clearance
GO NOT GO
TS/TR
mm
in
0.15
0.006
0.20
0.008
TX
mm
in
0.10
0.004
0.15
0.006
1. Ensure the decompressor is clear of the exhaust
valve rocker.
2. With the cylinder head cover removed, turn the
engine until the relevant piston is at the TDC
position on the firing stroke - both valves will be
closed.
3. Hold the adjusting screw (A) with a screwdriver and
slacken the locknut (B).
Turn the screw until the correct clearance has been
obtained.
Figure 2.18.1 Valve Clearance
4. Torque the locknut, while continuing to hold the
adjusting screw, to 21.0Nm (15.5lbf ft).
5. Re-check to ensure the clearance is correct.
6. Repeat the procedure for both valves in all cylinders.
Section 02
Engine Servicing and Adjustments
- valve clearance and decompressor
02.19 THE DECOMPRESSOR
The decompressor is fitted to the exhaust valve on
some engines. When the cylinder head cover is being
replaced care must be taken to ensure the lever is
vertical between the two stops.
The decompressor lever is spring loaded towards
the cylinder head and is located by a plain washer
and a split pin or circlip fitted through the
decompressor shaft. A seal, fitted on the outside of
the cylinder head, prevents oil seepage along the
spindle. On engine builds not fitted with a
decompressor the drilling in the cylinder head is
plugged with a dowel.
Removing the Decompressor
Remove the cylinder head cover. '
Remove the split pin or circlip, washer,
spring and adjusting screw.
Withdraw the decompressor lever from the
cylinder head.
Decompressor Adjustment
This adjustment should only be made when the
valve clearance is correctly adjusted.
After the decompressor has been set on TX engines
the maximum valve lift must not exceed 0.76mm
(0.030in).
1. Remove the cylinder head cover.
2. Turn the engine until the piston is at TDC. firing
stroke, for the cylinder being worked on.
TS and TR Engines
Figure 2.19.1 Decompressor Lever
3. Slacken the locknut (A) and adjust the screw (B)
until it just touches the exhaust valve rocker when
the lever is vertical.
4. Turn the screw half a turn clockwise so that it travels
towards the rocker.
5. Tighten the locknut whilst restraining the adjusting
screw.
TX Engines
6. Place the decompressor lever in the vertical
position.
7. Slacken the decompressor pin locknut and adjust
the pin to take up the valve clearance.
8. Turn the pin a further half a turn and tighten the
locknut.
All Engines
9. Replace the rocker cover taking care to ensure the
decompressor lever is vertical.