engine YAMAHA TTR50 2006 Service Manual

3 - 17
INSPADJ
6. Lubricate:
Drive chain
Drive chain lubricant:
SAE 10W-30 motor oil or
suitable chain lubricants
DRIVE CHAIN SLACK ADJUSTMENT
1. Elevate the rear wheel by placing the suit-
able stand under the engine.
2. Check: Drive chain slack a
In the center between the drive axle and
rear wheel axle.
Out of specification → Adjust.
NOTE:
Before checking and/or adjusting, rotate the
rear wheel through several revolutions and
check the slack several times to find the tight-
est point. Check and/or adjust chain slack with
rear wheel in this “tight chain ” position.
Drive chain slack:
35 ~ 45 mm (1.38 ~ 1.77 in)
3. Adjust:
Drive chain slack
Drive chain slack adjustment steps:
 Loosen the wheel axle nut 1 and locknuts
2 .
 Adjust chain slack by turning the adjusters
3 .
To tighten → Turn adjuster 3 clockwise a.
To loosen → Turn adjuster 3 counter-
clockwise b and push wheel forward.
 Turn each adjuster exactly the same
amount to maintain correct axle alignment.
(There are marks c on each side of chain
puller alignment.)
1 b
c
a
23
DRIVE CHAIN INSPECTION/
DRIVE CHAIN SLACK ADJUSTMENT

3 - 18
INSPADJDRIVE CHAIN SLACK ADJUSTMENT/
FRONT FORK INSPECTION/REAR SHOCK ABSORBER INSPECTION
NOTE:
Turn the adjuster so that the chain is in line
with the sprocket, as viewed from the rear.
CAUTION:
Too small chain slack will overload the
engine and other vital parts; keep the
slack within the specified limits.
 Tighten the wheel axle nut while pushing
down the drive chain.
T R..
Axle nut:
60 Nm (6.0 m  kg, 43 ft  lb)
 Tighten the locknuts.
T R..
Locknut:
7 Nm (0.7 m  kg, 5.1 ft  lb)
EC36C000
FRONT FORK INSPECTION
1. Inspect:
Front fork smooth action
Operate the front brake and stroke the
front fork.
Unsmooth action → Repair or replace.
EC36K000
REAR SHOCK ABSORBER INSPECTION
1. Inspect:
Swingarm smooth action
Abnormal noise/unsmooth action →
Grease the pivoting points or repair the
pivoting points.
Damage/oil leakage → Replace.

3 - 20
INSPADJWHEEL INSPECTION/
STEERING HEAD INSPECTION AND ADJUSTMENT
2. Inspect:
Bearing free play
Exist play → Replace.
STEERING HEAD INSPECTION AND
ADJUSTMENT
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Check:
Steering head
Grasp the bottom of the forks and gently
rock the fork assembly back and forth.
Free play → Adjust the steering head.
3. Check: Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action → Adjust the steering
head.
4. Adjust:
Steering head
Steering ring nut adjustment steps:
 Remove the front fender 1.
 Remove the handlebar 2, upper bracket
bolts 3, steering stem nut 4 and upper
bracket 5.
1
4
3
52

3 - 23
INSPADJ
ELECTRICAL/SPARK PLUG INSPECTION
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
Spark plug
2. Inspect: Electrode 1
Wear/damage → Replace.
 Insulator color 2
Normal condition is a medium to light tan
color.
Distinctly different color → Check the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure: Plug gap a
Use a wire gauge or thickness gauge.
Out of specification → Regap.
4. Clean the plug with a spark plug cleaner if necessary.
5. Tighten: Spark plug
NOTE:
 Before installing a spark plug, clean the gas-
ket surface and plug surface.
 Finger-tighten a the spark plug before torqu-
ing to specification b.
Spark plug gap:
0.6 ~ 0.7 mm (0.024 ~ 0.028 in)
Standard spark plug: CR7HSA (NGK)
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)

4 - 1
ENGFRONT FENDER, SEAT ASSEMBLY AND FUEL TANK
EC400000
ENGINE
EC4R0000
FRONT FENDER, SEAT ASSEMBLY AND FUEL TANK
Extent of removal:1 Front fender removal
2 Seat removal
3 Battery removal
4 Fuel tank removal
5 Air filter case removal
6 Bottom cover removal
Extent of removal Order Part name Q ’ty Remarks
FRONT FENDER, SEAT
ASSEMBLY AND FUEL TANK
REMOVAL
Preparation for removal Turn the fuel cock to “OFF ”.
1 Front fender 1
2 Seat assembly 1
3 Air scoop (left and right) 2
4 Battery cover 1
5 Battery coupler 1 Disconnect.
6 Battery band 1
7 Battery rubber cover 1
8 Battery 1
9 Fitting band 1
10 Fuel hose 1 Remove on fuel tank side.
1
2
3
43
4
5
5

4 - 13
ENGCYLINDER HEAD
4. Remove:Cylinder head
NOTE:
 Loosen the bolts and nuts in their proper
loosening sequence.
 Start by loosening each bolt and nut 1/2 turn
until all are loose.1
2
5
64
3
ASSEMBLY AND INSTALLATION
1. Install:
Cylinder head
2. Tighten: Nuts
 Bolts
NOTE:
 Apply the engine oil on the contact surfaces
of the nuts and copper washers.
 Apply the engine oil on the thread and con-
tact surface of the bolts.
 Follow the numerical order shown in the illus-
tration. Tighten the bolts and nuts in two
stages.
6
5
2
13
4
T R..22 Nm (2.2 m · kg, 16 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
3. Install:
Camshaft sprocket 1
Installation steps:
 Turn the crankshaft counterclockwise until
the “I” mark a on the rotor is aligned with
the stationary pointer b on the crankcase
cover.
 Align the “I” mark c on the camshaft
sprocket with the stationary pointer d on
the cylinder head.
 Fit the timing chain 2 onto camshaft
sprocket and install the camshaft sprocket
on the camshaft.
NOTE:
When installing the camshaft sprocket, keep
the timing chain as tense as possible on the
exhaust side.
b
a
1
2
c
d

4 - 16
ENGCAMSHAFT AND ROCKER ARMS
REMOVAL POINTS
Rocker arm shaft
1. Remove:Rocker arm shafts
NOTE:
Use a slide hammer bolt 1 and weight 2 to
slide out the rocker arm shafts.
Slide hammer bolt:
YU-01083-1/90890-01083
Weight: YU-01083-3/90890-01084
INSPECTION
Camshaft
1. Measure:
Cam 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:
Molybdenum disulfide oil
(onto the camshaft cam lobe)
 Engine oil
(onto the camshaft bearing)
2. Install: Camshaft 1

4 - 27
ENGCYLINDER AND PISTON
Piston pin
1. Inspect:Piston pin
Blue discoloration/grooves →
Replace, then inspect the lubrication sys-
tem.
2. Measure: Piston pin outside diameter
 Piston pin bore inside diameter
ASSEMBLY AND INSTALLATION
Piston
1. Install: Piston rings
(onto the piston)
NOTE:
 Be sure to install the piston rings so that the
manufacturer ’s marks or numbers are
located on the upper side of the rings.
 Lubricate the piston and piston rings liberally
with engine oil.
Measurement steps:

Measure the piston pin outside diameter
a .
If out of specification, replace the piston
pin.
Outside diameter (piston pin): 11.996 ~ 12.000 mm
(0.4723 ~ 0.4724 in)
:11.976 mm (0.4715 in)
 Measure the piston inside diameter b.
If out of specification, replace the piston.
Inside diameter (piston): 12.002 ~ 12.013 mm
(0.4725 ~ 0.4730 in)
: 12.043 mm (0.4741 in)

4 - 28
ENGCYLINDER AND PISTON
2. Position:Top ring
 2nd ring
 Oil ring
Offset the piston ring end gaps as shown.
a Top ring
b Upper oil ring rail
c Oil ring expander
d Lower oil ring rail
e 2nd ring
f 20 mm (0.79 in)
È Intake side
3. Install:
Piston 1
 Piston pin 2
 Piston pin clips 3
NOTE:
Apply engine oil onto the piston pin, piston
ring and piston.
 Be sure that the arrow mark
a on the piston
points to the exhaust side of the engine.
 Before installing the piston pin clip, cover the
crankcase with a clean rag to prevent the
piston pin clip from falling into the crankcase.
4. Lubricate: Piston
 Piston rings
 Cylinder
NOTE:
Apply a liberal coating of engine oil.
Cylinder
1. Install:
Dowel pins
 Gasket
 Cylinder 1
NOTE:
Install the cylinder with one hand while com-
pressing the piston rings with the other hand.
CAUTION:
 Be careful not to damage the timing chain
damper during installation.
 Pass the timing chain through the timing
chain cavity.
e a
ff
d cb120
˚
120 ˚ 120˚
È
New
1
New

4 - 29
ENGCLUTCH
CLUTCH
LS
E
E
E
T R..10 Nm (1.0 m • kg, 7.2 ft • Ib)T R..6 Nm (0.6 m •
kg, 4.3 ft • Ib)
T R..70 Nm (7.0 m •
kg, 50 ft • lb)
E
New
E
E
2 3
6
7
8
7
10
9
11
1314
16
25
45
20
20
191817
2728
29
2630
21
2423
22
12 15
31
1
New
T R..5 Nm (0.5 m •
kg, 3.6 ft • Ib)
(3)
Extent of removal: 1 Friction plate and clutch plate removal
2 Clutch housing removal
3 Clutch removal
Extent of removal Order Part name Q ’ty Remarks
CLUTCH REMOVAL
Preparation for removal Brake pedal and footrest assem- bly Refer to
“ENGINE REMOVAL ” section.
1 Clutch adjuster cover 1
2 Clutch adjuster locknut 1
3 Crankcase cover (right) 1
4 Dowel pin 2
5 Gasket 1
6 Clutch adjuster 1
7 Shift guide 2
8 Pawl holder 1
9 Shift arm 1
10 Pressure plate 1
213