Technical data

Repair instructions

Valves, grinding

(does not apply to engines with Nimonic

valves)*

* Note. Nimonic valves must not be ground.

Valve sealing angles:

Inlet: 29.5°

Exhaust: 44.5°

Check the valves before grinding them. Cracks and

damage to the valve head or bent valve stems always

mean that the valve must be replaced. Grind the seal-

ing surface as little as possible, just enough to make

it clean all the way round. If the valve head edge is

less than 1.2 mm wide after grinding on the 6(x) se-

ries, or 2.0 mm (inlet) and 1.0 mm (exhaust) on the

7(x) series, the valve must be replaced.

Always grind the mating surface in with grinding paste

(even on new valves and seats), and check mating

with indicator dye. If there is any lack of sealing, re-

grind the seat but not the valve. Then grind the valve

in with grinding paste and do a new check with indica-

tor dye.

Check the distance (A) between the plane of the

cylinder head and the valve head, as in item 1 under

the method for “Valve seat, replacement” on page 42.

Rocker mechanism,

renovation

Special tools: 6(x) series 9991876, 7(x) series

9992677.

Remove the circlips from the rocker shaft and remove

the rockers, bearing journals and springs.

Clean the components. Be especially careful with the

oil duct in the bearing journals, and the oil holes in the

rocker shaft and rockers.

Check the wear on the rocker shaft and the sealing of

the top hat plugs in the ends of the shaft. Also check

that the spherical part of the rocker arm is not de-

formed or worn. The threads on the adjustment

screws and locknuts must be undamaged. The hexa-

gon on the locknut must also be in good condition.

The spherical bearing surface of the rocker arm, which

is in contact with the valve/valve cap must not be un-

evenly worn or pitted. If there is minor wear, this can

be evened off by a grinder. If the rocker shaft hole is

worn oval, the rocker must be replaced.