Service Manual

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1. Check valve head for excessive deposit and gas leakage.
2. Remove carbon from valve head with wi-re brush.
3. Check valve head for warped face (A) dent on face and
margine
(B) of less than 0.5 mm (0.020 in.).
If valve head has above defect, replace valve,
N 0 T E : Excessive deposit is caused by leaded gasoline,
and deposit triggers gas leakage causing valve defects.
Therefore unleaded gasoline
is recommended.
4. Check valve stem for sticking, gummy deposit, discolora-
tion at area covered by valve guide, and excessive
corrosion.
5. Remove carbon from valve stem as well as head.
If valve stem
is worn excessively or does not move
smoothly in guide, replace valve.
N 0 T E : Sticking and discolorat ion are caused by over
heating of engine, or gas leakage from valve face. Therefore
such causes must be corrected as well as valve maintenance.
Gummy deposit
is caused by old or stale gasoline. Clean fuel
system and use fresh gasoline. Remove gasoline from fuel
system before long storage.
6. Check valve stem for worn stem end.
7. Grind worn stem end (C,D) squarely to stem shaft with
valve lapping guide
(E) and oil stone (F).
If length from stem end to groove is less than 3.8 mm
(0.15 in.) after grinding, replace valve.
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