Valves Tightness Test; Springs, Caps, Cotters Check - PIAGGIO 500 cc Service Manual

- If no troubles have been found after performing the
above check, it is possible to use the same valves. To
obtain a perfect sealing, it is recommendable to grind
the valve seats by using a fine grain lapping com-
pound. While grinding the valve seats, keep the head
with the valve axis horizontally to prevent the lapping
compound residuals from entering the valve guide
stem coupling. (see figure)
- To avoid scoring the contact surface do
Warning
not insist on turning the valve when the lapping com-
pound is finished. Carefully wash the head and the
valves with a product suitable for the type of lapping
compound used.
N.B.: Do not change the valves assembly position.

Valves tightness test

- Fit the valves in the head.
- Test alternately the intake and the exhaust valves
- The test must be performed after filling the manifold
with petrol. Check that the head is well in contact with
the screw caps by keeping them pressed with the
fingers.

Springs, caps, cotters check

- Check that the upper spring caps and the cotters
show no signs of anomalous wear.
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Thermal unit and timing system
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05_204
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