Turning the valve seats

Turning the valve seats

1. Turn the valve seats using suitable tools with the cylinder heads cold.

• After machining grind each valve in its housing as follows:

• coat the contact surfaces "A" and "B" of the valves and seats with abrasive paste (SIPAL AREXONS arbosilicium for valves).
• lubricate the valve stem with engine oil.
• fit the lower surface of the valve mushroom to the suction cup "C" of a pneumatic grinder.

• insert the valve in its guide and grind.

• after grinding, thoroughly clean the seat.

• When changing the valve guides, thus refacing and grinding the valve seats, it is advisable to check the valve tightness with the spark plugs in place, proceeding as follows:

• Fill the hollow of the combustion chamber with petrol.
• Admit low pressure air to the intake manifolds and check that no air bubbles form in the petrol.
• Check the tightness of the exhaust valves in the same way, admitting air to the exhaust manifolds.
• If any leaks are noted, make sure that the valves are perfectly settled in their seats and repeat the check; if the result is negative, grinding must be repeated.

Checking the clearance between cups and seats

1. Check that the diameter of the seats is within the specified limits.