2001 YAMAHA TTR125 fuel

3 - 10
INSP
ADJOIL PRESSURE INSPECTION/PILOT AIR SCREW
ADJUSTMENT/ENGINE IDLING SPEED ADJUSTMENT
OIL PRESSURE INSPECTION
1. Check:
lOil pressure
Checking steps:
lSlightly loosen the oil pressure check bolt
1.
lStart the engine and keep it idling until oil
starts to seep from the oil pressure check
bolt. If no oil comes out after one minute,
turn the engine off so it will not seize.
lCheck oil passages and oil pump for dam-
age or leakage.
lStart the engine after solving the prob-
lem(s) and recheck the oil pressure.
lTighten the oil pressure check bolt.
T R..
Oil pressure check bolt:
7 Nm (0.7 m • kg, 5.1 ft • lb)
PILOT AIR SCREW ADJUSTMENT
1. Adjust:
lPilot air screw 1
Adjustment steps:
NOTE:
To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot air screw has
been individually set at the factory. Before
adjusting the pilot air screw, turn it in fully
and count the number of turns. Record this
number as the factory-set number of turns
out.
lScrew in the pilot air screw until it is lightly
seated.
lBack out by the specified number of turns.
Pilot air screw:
2-1/2 ~ 3-1/2 turns out (example)
ENGINE IDLING SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it
up.
2. Attach:
lInductive tachometer
To spark plug lead.
3. Adjust:
lEngine idling speed

3 - 11
INSP
ADJ
VALVE CLEARANCE INSPECTION AND ADJUSTMENT
VALVE CLEARANCE INSPECTION AND
ADJUSTMENT
NOTE:
lThe valve clearance should be adjusted
when the engine is cool to the touch.
lThe piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
lSeat
lFuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4. Adjustment steps:
lAdjust the pilot air screw.
Refer to “PILOT AIR SCREW ADJUST-
MENT” section.
lTurn the throttle stop screw 1 until the
specified engine idling speed.
To increase idling speed ®
Turn the throttle stop screw 1 in a.
To decrease idling speed ®
Turn the throttle stop screw 1 out b.
Inductive tachometer:
YU-8036-B/90890-03113
Engine idling speed:
1,300 ~ 1,500 r/min
2. Remove:
lSpark plug
lIntake tappet cover 1
lExhaust tappet cover 2
lO-ring
3. Remove:
lTiming mark accessing screw 1
lCrankshaft end accessing screw 2
lO-ring

3 - 13
INSP
ADJ
VALVE CLEARANCE INSPECTION AND ADJUSTMENT
lMeasure the valve clearance.
lIf the clearance is incorrect, repeat above
steps until specified clearance is obtained.
6. Install:
lO-ring 1
lCrankshaft end accessing screw 2
lTiming mark accessing screw 3
NOTE:
Apply the lithium soap base grease on the O-
rings.
New
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
7. Install:
lO-ring 1
lExhaust tappet cover 2
lIntake tappet cover 3
NOTE:
Apply the lithium soap base grease on the O-
rings.
8. Install:
lSpark plug
lFuel tank
lSeat
Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section in the CHAP-
TER 4.
New
T R..18 Nm (1.8 m · kg, 13 ft · lb)
T R..18 Nm (1.8 m · kg, 13 ft · lb)
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)

3 - 27
INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
T R..
Ring nut (final tightening):
20 Nm (2.0 m • kg, 14 ft • lb)
lCheck the steering stem by turning it lock
to lock. If there is any binding, remove the
steering stem assembly and inspect the
steering bearings.
lInstall the rubber washer 8, upper ring
nut 9 and special washer 0.
NOTE:
lTighten the upper ring nut until it contacts
the rubber washer.
lInsert the special washer pawls into the
slots. If the slots are not aligned, tighten
the upper ring nut for alignment.
lInstall the upper bracket A, steering stem
nut B, cap C, handlebar D, upper han-
dlebar holder E, starter knob nut F and
number plate G.
NOTE:
lThe upper handlebar holder should be
installed with the punched mark a for-
ward.
lInsert the end of fuel breather hose H into
the hole of the starter knob stay.
CAUTION:
First tighten the bolts on the front side of
the handlebar holder, and then tighten
the bolts on the rear side.
T R..
Pinch bolt (upper bracket):
25 Nm (2.5 m • kg, 18 ft • lb)
Steering stem nut:
110 Nm (11.0 m • kg, 80 ft • lb)
Handlebar upper holder:
23 Nm (2.3 m • kg, 17 ft • lb)
Starter knob nut:
1 Nm (0.1 m • kg, 0.7 ft • lb)
Number plate:
7 Nm (0.7 m • kg, 5.1 ft • lb)

4 - 1
ENG

EC400000
ENGINE
EC4R0000
SEAT, FUEL TANK AND SIDE COVERS
Extent of removal:
1
Seat removal
2
Fuel tank removal
3
Side covers removal
4
Number plate removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removal
SEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Turn the fuel cock to “OFF”.
1 Seat 1
2 Air scoop (left and right) 2
3 Fuel hose 1 Remove on fuel tank side.
4 Fitting band 1
5 Bolt (fuel tank) 2
6 Fuel tank 1
7 Left side cover 1
8 Right side cover 1
9Number plate
1
13
4
2
3

SEAT, FUEL TANK AND SIDE COVERS
4

4 - 2
ENG

MUFFLER
MUFFLER
Extent of removal:
1
Muffler removal
Extent of removal Order Part name Q’ty Remarks
MUFFLER REMOVAL
Preparation for removal Right side cover Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Bolt (spark arrester) 3
2 Spark arrester 1
3 Nut (muffler) 2
4 Bolt (muffler) 1
5Muffler
1
1

4 - 3
ENG

CARBURETOR
CARBURETOR
Extent of removal:
1
Carburetor removal
Extent of removal Order Part name Q’ty Remarks
CARBURETOR REMOVAL
Preparation for removal Fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
1 Fuel hose 1
2 Over flow hose 1
3 Air vent hose 2
4 Starter plunger 1
5 Carburetor top cover 1
6 Clamp (air cleaner joint) 1 Loosen the screw (air cleaner joint).
7 Clamp (carburetor joint) 1 Loosen the screws (carburetor joint).
8Carburetor
1
1

4 - 5
ENG

CARBURETOR
HANDLING NOTE
At high altitudes, the atmospheric pressure is
lower. This can make the fuel mixture too rich,
leading to such problems as fouled.
Spark plugs and slow response at high engine
speeds. A special part, High Altitude Main Jet
1
#102.5 (620-1423A-71-A0) is available to
correct this.
EC463000
REMOVAL POINTS
Throttle valve
1. Remove:
l
Throttle valve
1

l
Spring (throttle valve)
2

l
Carburetor top cover
3

l
Throttle cable
4

NOTE:

While compressing the spring (throttle valve),
disconnect the throttle cable.
Pilot air screw
1. Remove:
l
Pilot air screw
1

NOTE:

To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot air screw has
been individually set at the factory. Before
removing the pilot air screw, turn it in fully and
count the number of turns. Record this number
as the factory-set number of turns out.