Checking The Valve Gear Timing; Valves Play Check/Adjustment; Checking Pressure At The End Of The Compression - PIAGGIO 500 cc Service Manual

General information and Maintenance

Checking the valve gear timing

- With a wrench of the TORX type, remove the timing
check plug located on the flywheel cover.
- Remove the transmission cover and relevant insula-
tion as described in Chapter 3-Automatic Transmis-
sion.
- Remove the head cover as described in Chapter 7-
Thermal Unit and Timing System.
- Turn the driving shaft by means of the driving pulley
until the reference mark on the magneto support
coincides with the mark on the flywheel cover (TDC).
- Make sure that the reference mark on the phonic
wheel is aligned with the mark on the head. If neces-
sary, turn the driving shaft accordingly.

Valves play check/adjustment

- Check the valves play after aligning the valve timing
reference marks as described in the previous section.
- Check that the valve-register play corresponds with
the indicated values by means of a feeler gauge. If the
valve play values, intake and exhaust respectively,
do not correspond with those indicated below, adjust
them by loosening the check nut and acting on the
register with a screwdriver, as shown in the figure.
0.15mm
Intake: 0.20 mm cold engine
Exhaust: 0.20 mm cold engine 0.15mm

Checking pressure at the end of the compression

- Remove the spark plug cap with the engine cold.
- Remove the spark plug.
- Fit a compression control gauge in the spark plug seat by means of a 10mm plug connection. Tighten to the
prescribed torque.
- Start the engine by means of the starting motor and with throttle body fully open until the gauge pointer stops. If
the pressure is between 8 - 11 bar, remove the tool and reassemble the spark plug.
- If the measured pressure is lower than the recommended values, check the engine revs number; if it is lower than
450 rpm, check the starting system; if the revs number is correct or slightly higher, check the timing. If no troubles
are found, proceed as follows:
- Check that the cylinder gasket is the right one.
- Check the thermal zone sealings (compression rings-valves).
Tightening torque:
Compression test connection: 10 N·m
1 - 8
01_226
05_225
05_233