- their seats are not so worn that the valve plate inserted into the cylinder head is located more than 1.5 mm below the surface of the cylinder head. To measure, put a metal ruler across the cylinder head and measure the distance;
- the cleaned head has no cracks, burnt spots or impact marks (in most cases they can only be seen after grinding);
- the intake valves still have the required flange thickness of at least 0.5 mm (see fig.).
The illustration shows the important dimensions for regrinding the valves: the thickness of the flange b at the inlet valve must be at least 0.5 mm. It is not measured at the inlet valve. The ring-shaped sealing surface must have a width a after grinding. For the intake valve, a is equal to 2.0 mm, for the exhaust valve - 2.4 mm.
Check the valve radial play in the valve guide first. The valves must not move more than 1.3 mm, otherwise the valve guides must be replaced.
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