Checks And Overhaul; Cylinder Heads; Valves - Guides - Seats - Kohler KD 477-2 Workshop Manual

IX

CHECKS AND OVERHAUL

5
6
7
8
- 18 -

Cylinder heads

Details of fig. 5:
1. Cylinder head - 2. Pipe - 3. O-Ring - 4. Rockerarms - 5. Rockers -
6. Cotters - 7. Plates - 8. Springs - 9. Guides - 10. Seats - 11. Valves
- 12. Tappets - 13. Camshaft.
The heads are of aluminium with inserted guides and valve seats in
cast iron. Make sure there are no cracks or imperfections. Should it
be so, replace according to the instructions given in the spare parts
catalogue.
Never remove head while still hot in order to avoid defor-
mation.

Valves - Guides - Seats

Clean the valves with a wire brush and renew them if the valve heads
are deformed, cracked or worn.
Check clearance between valve and guide with a micrometer on
stem B (fig. 7) and with a go/no go gauge as shown in fig. 6 (tool cod.
00365R0450).
Change the guide if the maximum gauge diameter passes through it,
as it has passed the maximum permissible wear.
After having fitted the new guide, check exact diameter using the "go"
end of the gauge and if necessary grind it to the dimensions indicated
in the table using the adjustable grinder (tool cod. 00365R0850).
Engine Guide
Inlet
KD 477-2
Outlet
Fitting of new guides always requires grinding of the valve seats (see
page 19).
Valve guides with an external diameter increased by 0.10 mm are
available.
If the inlet clearance between valve and guide is lower than 0.08 mm
and the outlet clearance is lower than, 0.10 mm, the wear on B is
less than 0.03 mm and A is more than 0.05 mm, recondition the val-
ve by grinding face P to 45° (fig. 7).
As a result of prolonged engine operation, the hammering of the val-
ves on their seats at high temperature causes the face of the seats to
harden and hand grinding is made difficult. It is thus necessary to re-
move the hardened surface with a 45° cutter mounted on a valve seat
grinding tool (fig. 8). Final fitting can then be carried out manually with
the cutters listed below.
Cut dimensions for valve seats
Inlet
Engine
A x B
KD 477-2 40 x 12 mm
KD 477-2 Workshop Manual_cod. ED0053029370_1° ed_ rev. 00
Ø Guide Ø Gauge mm
mm
go
7,000 ÷ 7,010 7,000
Outlet
Ø guide A x B
7 mm 38 x 12 mm
no go
7,079
Ø guide
7 mm