72
If seats are beyond repair, it is necessary to change the
complete cylinder as the seats are not replaceable.
Check the valve seats for pitting etc, the valves are marked
‘E’ (exhaust) and ‘I’ (inlet). If the valve guides are worn,
valves with oversize stems are available and the guides
should be reamed out to take these. Grind in the valve
using tool no. 88841015 (Fig 4).
Check that the valve head is within dimensions shown in
Fig 5.
Thickness ‘A’ should not be less than 0,8 mm.
Valve seat should not exceed 1-2 mm (0.039”-0.078”) in
depth.
Check that the valve springs are not cracked or broken
and that free, length is not less than 24 mm (15/16”).
Replace springs if necessary.
Remove all traces of grinding paste and refit valves in
their correct position, refit springs and securing caps
(Fig 6).
Check the tappet clearance and set to 0,10-0,20 mm
(.006”-.009”). The clearance is obtained by carefully
grinding the stem to shorten valve length.
When checking the valve clearance on engines fitted with
compression release, care must be taken to ensure that
the reading is taken with the camshaft at the point where
the cam is not in contact with the tappet (i.e. TDC
compression stroke).
Check valve sealing by holding block in position (Fig 7)
and filling the ports with petrol and checking the valve
seats for leaks.
Fig. 4
Fig. 5
Fig. 6
Fig. 7
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