Man D 2842 LE 620, Repair Manual

Page: 101 / 180

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Refacing valves
99
Fig. 1
Apply abrasive paste to the tapered area of the
valve seat.
Lubricate the valve guide and insert the valve.
Fig. 2
Use a valve grinder to reface the valve seat by ap-
plying moderate axial pressure and describing a
turning motion.
Note:
Keep the valve stem and the valve guide
free of abrasive paste.
Fig. 3
The valve seat must have a faultless, contained
grinding pattern.
The grinding pattern width is correct if the valve
seat insert is in order.
À
Valve tapered area
Á
Valve seat
Fig. 4
À
Valve seat insert
Á
Valve
Â
Valve seat too wide
Ã
Valve seat good
Note:
Valve seats which are too wide tend to
accumulate coking residues,
− valves start to leak −
Valve seats which are to narrow prevent
rapid dissipation of heat from the valve
plate to the cylinder head,
− valves burn −
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