50
Valve seat, replacing
Special tools: 999 2479, 998 9876
1
valve seats should be replaced when the when the
distance (A), measured to the new valve exceeds (for
the 42A/B when the distance is less than):
31/32/41/42/43 42A/B* 44/300
Intake 0.65 mm 0.05 mm 1.60 mm
Exhaust 0.65 mm 0.05 mm 1.50 mm
* For the 42A/B that the valve crown is above the cylinder head
surface.
2
The old valve seat is removed by grinding two break-
age points in the seat and then breaking it with a
chisel. Alternatively an scrapped valve can be spot-
welded to the seat and then the seat is beaten out.
Grind down the scrapped valve crown so that it can
be stuck down just under the edge of the valve seat.
MIG or MAG weld, cover the surrounding area so that
any welding drops do not fasten anywhere.
IMPORTANT! Be careful so that the cylinder
head is not damaged.
Repair Instructions
3
Clean the seat position and check that there are no
cracks.
Measure the diameter of the valve seat position. De-
cide using the measurement whether a standard or
oversized seat is needed.
Carry out any work required on the valve seat posi-
tion.
Cool the seat with dry ice to –60 to –70°C and if ne-
cessary heat the cylinder head with warm water by
rinsing or similar. Press in the seat with a drift.
NOTE! Turn the seat the correct way, valve face out-
wards!
The work must be carried out as quickly as possible
so that the largest possible temperature difference is
retained.
Work the seat to the correct angle and width.
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