Yamaha YFM250BT 2004 Manual

LIT-11616-18-41 4XE-F8197-13
YFM250BT
SUPPLEMENTARY
SERVICE MANUAL

FOREWORD
This Supplementary Service Manual has been prepared to introduce new service and data for the
YFM250BT. For complete service information procedures it is necessary to use this Supplementary
Service Manual together with the following manual.
YFM250XL(C) SERVICE MANUAL: LIT-11616-12-01 (4XE-F8197-10)
YFM250XN SUPPLEMENTARY SERVICE MANUAL: LIT-11616-14-17 (4XE-F8197-11)
YFM250XP SUPPLEMENTARY SERVICE MANUAL: LIT-11616-15-03 (4XE-F8197-12)
YFM250BT
SUPPLEMENTARY
SERVICE MANUAL
©2004 by Yamaha Motor Corporation, U.S.A.
First edition, July 2004
All rights reserved.
Any reproduction or unauthorized use
without the written permission of
Yamaha Motor Corporation, U.S.A.
is expressly prohibited.
Printed in U.S.A.
LIT-11616-18-41

EBS00002
NOTICE
This manual was produced by the Yamaha Motor Company primarily for use by Yamaha dealers
and their qualified mechanics. It is not possible to include all the knowledge of a mechanic in one
manual, so it is assumed that anyone who uses this book to perform maintenance and repairs on
Yamaha machine has a basic understanding of the mechanical ideas and the procedures of
machine repair. Repairs attempted by anyone without this knowledge are likely to render the
machine unsafe and unfit for use.
Yamaha Motor Company, Ltd. is continually striving to improve all its models. Modifications and sig-
nificant changes in specifications or procedures will be forwarded to all authorized Yamaha dealers
and will appear in future editions of this manual where applicable.
NOTE:
_
Designs and specifications are subject to change without notice.
EBS00003
IMPORTANT INFORMATION
Particularly important information is distinguished in this manual by the following notations.
The Safety Alert Symbol means ATTENTION! BECOME ALERT! YOUR
SAFETY IS INVOLVED!
Failure to follow WARNING instructions could result in severe injury or death to
the machine operator, a bystander or a person checking or repairing the
machine.
A CAUTION indicates special precautions that must be taken to avoid damage
to the machine.
A NOTE provides key information to make procedures easier or clearer.
WARNING
CAUTION:
NOTE:

EBS00004
HOW TO USE THIS MANUAL
MANUAL ORGANIZATION
This manual consists of chapters for the main categories of subjects. (See “symbols”)
1st title 1: This is the title of the chapter with its symbol in the upper right corner of each page.
2nd title 2: This title indicates the section of the chapter and only appears on the first page of each
section. It is located in the upper left corner of the page.
3rd title 3: This title indicates a sub-section that is followed by step-by-step procedures accompa-
nied by corresponding illustrations.
EXPLODED DIAGRAMS
To help identify parts and clarify procedure steps, there are exploded diagrams at the start of each
removal and disassembly section.
1. An easy-to-see exploded diagram 4is provided for removal and disassembly jobs.
2. Numbers 5are given in the order of the jobs in the exploded diagram. A number that is enclosed
by a circle indicates a disassembly step.
3. An explanation of jobs and notes is presented in an easy-to-read way by the use of symbol marks
6. The meanings of the symbol marks are given on the next page.
4. A job instruction chart 7accompanies the exploded diagram, providing the order of jobs, names
of parts, notes in jobs, etc.
5. For jobs requiring more information, the step-by-step format supplements 8are given in addition
to the exploded diagram and the job instruction chart.

EBS00005
SYMBOLS
The following symbols are not relevant to
every machine.
Symbols 1to 9indicate the subject of each
chapter.
1General information
2Specifications
3Periodic checks and adjustments
4Engine
5Carburetion
6Drive train
7Chassis
8Electrical
9Troubleshooting
Symbols 0to Findicate the following.
0Filling fluid
ALubricant
BSpecial tool
CTorque
DWear limit, clearance
EEngine speed
FElectrical data (Ω, V, A)
Symbols Gto Min the exploded diagrams
indicate the types of lubricants and lubrication
points.
GApply engine oil
HApply gear oil
IApply molybdenum disulfide oil
JApply wheel bearing grease
KApply lithium-soap-based grease
LApply molybdenum disulfide grease
MApply silicon grease
Symbols Nto Oin the exploded diagrams
indicate where to apply a locking agent Nand
when to install a new part O.
NApply the locking agent (LOCTITE®)
OReplace
12
34
56
78
90
AB
CD
EF
GHI
J
NO
GEN
INFO SPEC
CHK
ADJ ENG
CARB
DRIV
CHAS
–+
ELEC
TRBL
SHTG
T
R
.
.
EGM
BLS MS
KLM
LT
New

CONTENTS
SPECIFICATIONS .............................................................................................1
GENERAL SPECIFICATIONS ....................................................................1
MAINTENANCE SPECIFICATIONS ...........................................................2
ENGINE ................................................................................................2
CHASSIS ..............................................................................................3
ELECTRICAL ........................................................................................4
CABLE ROUTING .......................................................................................5
PERIODIC CHECKS AND ADJUSTMENTS ...................................................14
INTRODUCTION .......................................................................................14
PERIODIC MAINTENANCE/LUBRICATION .............................................14
SEAT, CARRIERS, FENDERS AND FUEL TANK ....................................16
SEAT, FRONT CARRIER, FRONT BUMPER
AND FRONT FENDER ......................................................................16
REAR CARRIER AND REAR FENDER ..............................................18
FUEL TANK ........................................................................................20
FOOTREST BOARDS ...............................................................................21
ENGINE .....................................................................................................22
ADJUSTING THE STARTER CABLE .................................................22
CHASSIS ...................................................................................................23
ADJUSTING THE REAR BRAKE .......................................................23
ADJUSTING THE SELECT LEVER CONTROL CABLE
AND SHIFT ROD ...............................................................................25
ADJUSTING THE HEADLIGHT BEAM ...............................................26
REPLACING A HEADLIGHT BULB ....................................................26
ENGINE ...........................................................................................................28
ENGINE REMOVAL ..................................................................................28
SELECT LEVER ASSEMBLY .............................................................28
CARBURETION ...............................................................................................29
CARBURETOR .........................................................................................29
CHASSIS .........................................................................................................32
REAR BRAKE ...........................................................................................32
STEERING SYSTEM ................................................................................34
STEERING STEM ...............................................................................34
REMOVING THE REAR BRAKE SWITCH .........................................36
INSTALLING THE HANDLEBAR ........................................................36

ELECTRICAL ..................................................................................................37
ELECTRICAL COMPONENTS ..................................................................37
YFM250BT WIRING DIAGRAM

–1 –
SPEC
GENERAL SPECIFICATIONS
SPECIFICATIONS
GENERAL SPECIFICATIONS
Item Standard
Model code: 1P01
Dimensions:
Overall length 1,916 mm (75.4 in)
Overall width 1,038 mm (40.9 in)
Overall height 1,118 mm (44.0 in)
Seat height 772 mm (30.4 in)
Wheelbase 1,170 mm (46.1 in)
Minimum ground clearance 150 mm (5.9 in)
Minimum turning radius 2,900 mm (114 in)
Basic weight:
With oil and full fuel tank 216 kg (476 lb)
Carburetor:
Type/quantity BSR33/1
Manufacturer MIKUNI
Tire:
Type Tubeless
Size front AT22 ×7-10
rear AT22 ×10-10
Manufacturer front MAXXIS
rear MAXXIS
Type front M905
rear M906
Electrical:
Ignition system DC C.D.I.
Generator system A.C. magneto
Battery type CB14A-A2
Battery capacity 12 V 14 AH
Bulb wattage ×quantity:
Headlight 12 V 30 W/30 W × 2
Tail/brake light 12 V 5 W/21 W × 1
Indicator lights:
Neutral 12 V 1.7 W ×1
Reverse 12 V 1.7 W ×1

– 2 –
SPEC
MAINTENANCE SPECIFICATIONS
MAINTENANCE SPECIFICATIONS
ENGINE
Tightening torques
Item Standard Limit
Carburetor:
I. D. mark 1P01 00 ----
Main jet (M.J) #93.8 ----
Main air jet (M.A.J) #70 ----
Jet needle (J.N) 5EP17-2 ----
Needle jet (N.J) P-2M (826) ----
Pilot air jet (P.A.J.1) #80 ----
Pilot air jet (P.A.J.2) 1.3 ----
Pilot outlet (P.O) 0.8 ----
Pilot jet (P.J) #20 ----
Bypass 1 (B.P.1) 0.8 ----
Bypass 2 (B.P.2) 0.8 ----
Bypass 3 (B.P.3) 0.8 ----
Valve seat size (V.S) 2.0 ----
Starter jet (G.S.1) #62.5 ----
Starter jet (G.S.2) 0.9 ----
Throttle valve size (Th.V) #100 ----
Float height (F.H) 12.0 ~ 14.0 mm (0.47 ~ 0.55 in) ----
Fuel level (F.L) 4.0 ~ 5.0 mm (0.16 ~ 0.20 in) ----
Engine idle speed 1,400 ~ 1,500 r/min ----
Intake vacuum 30.7 kPa (230 mmHg, 9.06 inHg) ----
Part to be tightened Part
name
Thread
size Q’ty Tightening torque Remarks
Nm m · kg ft · lb
Starter motor holding bracket Screw M6 2 7 0.7 5.1
Bearing retainer 1
(bearing housing) Nut M50 1 80 8.0 58 LT
Drive select lever unit and frame Bolt M8 2 23 2.3 17
Drive select lever component:
Lever component Bolt M6 1 14 1.4 10
Middle drive pinion gear Nut M16 1 90 9.0 65 Stake
Shift guide stopper bolt Bolt M8 1 20 2.0 14

–3 –
SPEC
MAINTENANCE SPECIFICATIONS
CHASSIS
Tightening torques
Item Standard Limit
Brake lever and brake pedal:
Front brake lever free play (at lever pivot) 0 mm (0 in) ----
Rear brake lever free play (at lever pivot) 5 ~ 7 mm (0.20 ~ 0.28 in) ----
Brake pedal free play 20 ~ 30 mm (0.79 ~ 1.18 in) ----
Throttle lever free play 3 ~ 5 mm (0.12 ~ 0.20 in) ----
Part to be tightened Part
name Thread size Q’ty Tightening torque Remarks
Nm m ·kg ft ·lb
Steering knuckle and tie-rod end Nut M12 ×1.25 2 30 3.0 22
Tie-rod and locknut Nut M12 ×1.25 4 40 4.0 29
Steering shaft and tie-rod end Nut M12 ×1.25 2 30 3.0 22
Front carrier and frame Bolt M8 ×1.25 4 34 3.4 24
Front carrier and front fender Bolt M6 ×1.0 2 7 0.7 5.1
Front carrier and front bumper Bolt M8 ×1.25 2 34 3.4 24
Front bumper and frame Bolt M8 ×1.25 4 34 3.4 24
Front bumper, front fender and
front grill Bolt M6 ×1.0 2 7 0.7 5.1
Front fender and front grill Bolt M6 ×1.0 2 7 0.7 5.1
Rear carrier and frame Bolt M8 ×1.25 4 34 3.4 24
Rear carrier and rear fender Bolt M6 ×1.0 2 7 0.7 5.1
Rear fender, air filter case and
frame Bolt M6 ×1.0 2 7 0.7 5.1
Rear fender and frame Bolt M6 ×1.0 1 7 0.7 5.1
Battery holding bracket Bolt M6 ×1.0 2 7 0.7 5.1
Footrest bracket and frame
(left and right) Bolt M10 ×1.25 4 65 6.5 47
Bolt M8 ×1.25 4 34 3.4 24
Footrest, footrest board and foot-
rest bracket (left and right) Bolt M6 ×1.0 4 7 0.7 5.1

–4 –
SPEC
MAINTENANCE SPECIFICATIONS
ELECTRICAL
Item Standard Limit
C.D.I.:
Magneto model/manufacturer F4T259/MITSUBISHI ----
Pickup coil resistance/color 189 ~ 231 Ωat 20 °C (68 °F)/
White/Green –White/Red
----
Rotor rotation direction detection coil resis-
tance/color
0.065 ~ 0.080 Ωat 20 °C (68 °F)/
Red –White/Blue
----
C.D.I. unit model/manufacturer F8T38683/MITSUBISHI ----
Electric starter system:
Type Constant mesh type ----
Starter motor:
Model/manufacturer 5XG/MORIC TAIWAN ----
Output 0.4 kW ----
Armature coil resistance 0.0144 ~ 0.0176 Ωat 20 °C
(68 °F)
----
Brush overall length 10 mm (0.4 in) 3.5 mm
(0.14 in)
Spring force 563 ~ 844 g (5.52 ~ 8.28 N) ----
Commutator diameter 22 mm (0.87 in) 21 mm
(0.83 in)
Mica undercut 1.5 mm (0.059 in) ----
Starter relay:
Model/manufacturer MS5F-721/JIDECO ----
Amperage rating 180 A ----
Coil winding resistance/color 4.2 ~ 4.6 Ωat 20 °C (68 °F)/
Blue/Black –Blue/White
----

–5 –
SPEC
CABLE ROUTING
1Rear brake light switch lead
2Starter cable
3Rear brake cable
4Lower bracket cable guide
5Front brake hose
6Front brake light switch lead
7Throttle cable
8Reverse indicator light
9Neutral indicator light
0Fuel tank breather hose
AHandlebar switch assembly lead
BRectifier/regulator
CABLE ROUTING

–6 –
SPEC
CABLE ROUTING
ÈDo not route the handlebar switch assembly
lead through the lower bracket cable guide.
ÉFasten the front brake light switch lead to the
handlebar with the plastic band.
ÊFaster the front brake light switch lead and front
brake hose to the handlebar with the plastic
band.
ËRoute the fuel tank breather hose through the
hole in the handlebar cover and then to the right
of the handlebar (below the handlebar, not over
it). Then, pass the hose through the cable guide.
ÌFasten the handlebar switch assembly lead, rear
brake light switch lead, and starter cable to the
handlebar with the plastic bands.
ÍFasten the handlebar switch assembly lead to
the handlebar with the plastic band.
ÎFasten the rear brake light switch lead, front
brake light switch lead, and handlebar switch
assembly lead with the plastic band.
ÏFasten the headlight leads to the frame with the
clamp.

–7 –
SPEC
CABLE ROUTING
1Headlight lead
2Lower bracket cable guide
3Indicator light lead
4Main switch lead
5Indicator light
6Main switch
7Fuel tank breather hose
8Carburetor overflow hose
9Reverse switch lead
0Neutral switch lead
ANegative battery lead
BA.C. magneto lead
CStarter cable
DRear brake cable
ESelect lever control cable
FThrottle cable
GStarter motor lead

–8 –
SPEC
CABLE ROUTING
ÈFasten the headlight lead to the front bumper
with the plastic band.
ÉRoute the main switch lead and indicator light
lead to the side of the lower bracket cable guide.
ÊFasten the starter cable to the frame with the
plastic locking tie.
ËInsert the carburetor air vent hose, rear brake
breather hose, and final gear case breather
hose into the air duct after routing them through
the fuel tank grommet.
ÌRoute the carburetor overflow hose between the
engine and upper rear engine mount and then
between the engine and swingarm. Make sure
that the hose is not pinched.
ÍRoute the reverse switch lead and neutral switch
lead to the right of the rear arm boot.
ÎFasten the starter motor lead to the frame with
the plastic clamp. Route the starter motor lead
over the throttle cable and rear brake cable.
ÏBend the cable guide after routing the cables.

–9 –
SPEC
CABLE ROUTING
1A.C. magneto lead couplers
2Wire harness
3Starter motor lead
4Tail/brake light lead
5Battery breather hose
6Final gear case breather hose
7Negative battery lead
8Ground lead
9Carburetor air vent hose
0Rear brake breather hose
ARear brake light switch lead
BRear brake cable
CA.C. magneto lead
ÈMake sure that the starter motor lead has no
slack.
É0 mm (0 in)
ÊFasten the starter motor lead and wire harness
to the frame with the plastic band.

–10 –
SPEC
CABLE ROUTING
ËFasten the negative battery lead with the plastic
clamp.
ÌFasten the tail/brake light lead and negative bat-
tery lead with the plastic locking tie.
ÍFasten the negative battery lead with the plastic
clamp.
Î40 ~ 50 mm (1.6 ~ 2.0 in)
ÏFasten the starter motor lead and wire harness
to the frame with the plastic clamp.
ÐRoute the rear brake cable and rear brake
breather hose through the cable guide.
Ñ100 mm (4.0 in)
ÒRoute the rear brake breather hose through the
cable guide.
ÓRoute the final gear case breather hose through
the cable guide.
ÔFasten the rear brake cable and rear brake
breather hose to the swingarm with the plastic
clips.

–11 –
SPEC
CABLE ROUTING
1Battery breather hose
2Rear brake cable
3Select lever control cable
4Spark plug cap
5Ignition coil
6Ignition coil leads
7Starter motor lead
8Rear brake light switch
9Rear brake breather hose
ÈFasten the battery breather hose to the frame
with the plastic band.
ÉFasten the starter motor lead to the frame with
the plastic clamps.
Ê50 ~ 60 mm (2.0 ~ 2.4 in)
ËFasten the battery breather hose to the frame
with the plastic clamps.

–12 –
SPEC
CABLE ROUTING
1Positive battery lead
2Battery
3Tail/brake light lead
4Negative battery lead
5CDI unit
6Starter relay
7Wire harness
8Starter motor lead
9Carburetor air vent hose
0Final gear case breather hose
ARear brake breather hose
ÈFasten the wire harness, starter motor lead, and
select lever control cable to the frame with the
plastic band.
É5 mm (0.2 in)
ÊFasten the positive battery lead to the rear
fender with the plastic clamps.
ËMake sure that the grommet is installed with the
mark facing forward.

–13 –
SPEC
CABLE ROUTING
1Headlight leads
2Wire harness
3Starter motor lead
4Rear brake cable
5Throttle cable
6Starter cable
7Select lever control cable
8Rectifier/regulator
ÈFasten the wire harness to the frame with the
plastic clamps.
ÉMake sure the starter motor lead and wire har-
ness do not contact the ignition coil.
Ê50 mm (2.0 in)
ËRoute the throttle cable, select lever control
cable and rear brake cable through the cable
guide. Make sure that the throttle cable is routed
to the inside of the rear brake cable.
ÌFasten the wire harness, starter motor lead, and
ignition coil lead to the frame with the plastic
band.