2001 YAMAHA TTR90 length

4 - 14
ENGCAMSHAFT AND ROCKER ARMS
REMOVAL POINTS
Rocker arm shaft
1.Remove:
lRocker arm shafts
NOTE:
Use a slide hammer bolt 1 and weight 2 to
slide out the rocker arm shafts.
Slide hammer set:
YU-1083-A
Slide hammer bolt:
90890-01085
Weight:
90890-01084
INSPECTION
Camshaft
1.Measure:
lCam lobes length a and b
Out of specification ® Replace.
Cam lobes length limit:
Intake:
a 25.328 mm (0.9972 in)
b 20.934 mm (0.8242 in)
Exhaust:
a 25.186 mm (0.9916 in)
b 20.947 mm (0.8247 in)
ASSEMBLY AND INSTALLATION
1.Apply:
lMolybdenum disulfide oil
(onto the camshaft cam lobe)
lEngine oil
(onto the camshaft bearing)
2.Install:
lCamshaft 1

4 - 18
ENGVALVES AND VALVE SPRINGS
Valve spring
1.Measure:
lValve spring free length a
Out of specification ® Replace.
2.Measure:
lSpring tilt a
Out of specification ® Replace.
Free length (valve spring):
Intake:
28.32 mm (1.11 in)
: 26.9 mm (1.06 in)
Exhaust:
28.32 mm (1.11 in)
: 26.9 mm (1.06 in)
Spring tilt limit:
Intake:
2.5˚/1.2 mm (0.05 in)
Exhaust:
2.5˚/1.2 mm (0.05 in)
Valve seat
1.Measure:
lValve seat width a
Out of specification ® Reface the valve
seat.
Valve seat width:
Intake:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Measurement steps:
lApply Mechanic’s blueing dye (Dykem) b
to the valve face.
lInstall the valve into the cylinder head.
lPress the valve through the valve guide
and onto the valve seat to make a clear
pattern.
lMeasure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
lIf the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat
must be refaced.

4 - 31
ENG

CLUTCH
EC484600
Clutch plate
1. Measure:
l
Clutch plate warpage
Out of specification
®
Replace clutch
plate as a set.
Use a surface plate
1
and thickness
gauge
2
.
EC484400
Clutch spring
1. Measure:
l
Clutch spring free length
a

Out of specification
®
Replace springs
as a set.
Push rod
1. Measure:
l
Push rod #2 bend
Out of specification
®
Replace.
Warp limit:
0.2 mm (0.008 in)
Clutch spring free length
Standard Limit
26.2 mm
(1.03 in)24.2 mm
(0.95 in)
Bending limit:
0.5 mm (0.02 in)
Primary clutch
1. Measure:
l
Primary clutch housing inside diameter
Out of specification
®
Replace.
Primary clutch housing inside
diameter:
105 mm (4.13 in)
: 106 mm (4.17 in)
2. Measure:
l
Clutch shoe groove depth
a

Out of specification
®
Replace.
Clutch shoe groove depth:
1.0 ~ 1.3 mm (0.039 ~ 0.051 in)
: 0.1 mm (0.004 in)