Yamaha XT550J - Cylinder Head; Valves, Valve Guides, Valve Seats, and Valve Springs

2. Remove the valves. Mark each valve so
it will be reinstalled in the same cylinder
head.
NOTE: ______ __ ____ ______ ____ __
Deburr any deformed valve stem end. Use an
oil stone to smoC'th the stem end. This will
help prevent damage to the valve guide dur-
ing
valve removal.
~ -----+---? DEBURR
----,f---- VALVE STEM
3. Using a rounded scraper, remove the
carbon deposits from the combustion
chamber. Take care
to avoid damaging
the spark
plug threads and valve seats.
Do not use a sharp instrument. Avoid
scratching the
aluminum.
4. Check the cylinder head warpage with a
straightedge
as shown.
The warpage
should not exceed the
specified
limit; if necessary, resurface
the
cylinder head. If the warpage ex-
ceeds
allowable limit, the cylinder head
should be replaced with a new one.
Cylinder head warpage:
less than 0.03 mm (0.0012 in)
Allowable limit: 0.25 mm (0 . 010 in)
3-13
C. Valves, Valve Guides, Valve Seats,
and Valve Springs
1. Check the valve face and the stem end
for wear.
If the valve face and/ or the
stem end are pitted
Or worn, regrind the
valve with a valve refacer. Replace the
valve if any dimension exceeds the
specifications
in the illustration.
INTAKE/EXHAUST
VALVE
;:11-
t
--
·MINIMUM THICKNESS
(SERVICE LIMIT)
0.7 mm (0.028 in)
-
0.5 mm (0.020 in)
--
MINIMUM LENGTH (SERVICE LIMIT)
4.0 mm (0.157 in)
2. Valve stem wear must be measured and
then combined with
valve guide meas-
urements
to obtain guide clearance.
This clearance must be within tole-
rances. If it exceeds the maximum limit,
then replace either or both valve and
guide
as necessary.
----------
Valve Stem Clearance Maximum
Intake
0.010 - 0.037 mm
0.10mm
(0.0004 - 0.0015 in)
(0.004 in)
0.030
- 0. 057 mm
0.12mm
Exhaust
(0.0012 - 0.0022 in)
(0.005 in)