Yamaha YZF-R1 2012, Service Manual, Page: 284 / 556

VALVES AND VALVE SPRINGS
5-33
TIP
For the best lapping results, lightly tap the
valve seat while rotating the valve back and
forth between your hands.
e. Apply a fine lapping compound to the valve
face and repeat the above steps.
f. After every lapping procedure, be sure to
clean off all of the lapping compound from
the valve face and valve seat.
g. Apply Mechanic’s blueing dye (Dykem) “b”
onto the valve face.
h. Install the valve into the cylinder head.
i.
Press the valve through the valve guide
and onto the valve seat to make a clear
impression.
j. Measure the valve seat width “c” again. If
the valve seat width is out of specification,
reface and lap the valve seat.
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EAS24310
CHECKING THE VALVE SPRINGS
The following procedure applies to all of the
valve springs.
1. Measure:
• Valve spring free length “a”
Out of specification
→
Replace the valve
spring.
2. Measure:
• Compressed valve spring force “a”
Out of specification
→
Replace the valve
spring.
Valve spring free length
Free length (intake)
39.33 mm (1.55 in)
Limit
37.36 mm (1.47 in)
Free length (exhaust)
37.96 mm (1.49 in)
Limit
36.06 mm (1.42 in)
Installed compression spring
force (intake)
187.00–215.00 N (19.07–21.92
kgf, 42.04–48.33 lbf)
Installed compression spring
force (exhaust)
185.00–213.00 N (18.86–21.72
kgf, 41.59–47.88 lbf)
Installed length (intake)
34.50 mm (1.36 in)
Installed length (exhaust)
33.00 mm (1.30 in)