Kawasaki KX 125 2003-2008, KX 250 2003 2008 Service manual
KX125
KX250
Motorcycle
Service Manual
Quick Reference Guide
General Information 1 j
Periodic Maintenance 2 j
Fuel System 3 j
Cooling System 4 j
Engine Top End 5 j
Engine Right Side 6 j
Engine Removal/Installation 7 j
Engine Bottom End/Transmission 8 j
This quick reference guide will assist
you in locating a desired topic or procedure.
•Bend the pages back to match the
black tab of the desired chapter number with the black tab on the edge at
each table of contents page.
•Refer to the sectional table of contents
for the exact pages to locate the specific topic required.
Wheels/Tires 9 j
Final Drive 10 j
Brakes 11 j
Suspension 12 j
Steering 13 j
Electrical System 14 j
Appendix 15 j
KX125
KX250
Motorcycle
Service Manual
All rights reserved. No parts of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic mechanical photocopying, recording or otherwise,
without the prior written permission of Quality Assurance Division/Consumer Products & Machinery
Company/Kawasaki Heavy Industries, Ltd., Japan.
No liability can be accepted for any inaccuracies or omissions in this publication, although every possible
care has been taken to make it as complete and accurate as possible.
The right is reserved to make changes at any time without prior notice and without incurring an obligation
to make such changes to products manufactured previously. See your Motorcycle dealer for the latest
information on product improvements incorporated after this publication.
All information contained in this publication is based on the latest product information available at the time
of publication. Illustrations and photographs in this publication are intended for reference use only and may
not depict actual model component parts.
© 2002 Kawasaki Heavy Industries, Ltd., 7th Edition (1) : Mar. 22, 2007 (K)
LIST OF ABBREVIATIONS
A ampere(s) lb pound(s)
ABDC after bottom dead c enter mmeter(s)
AC alternating current min minute(s)
ATDC after top dead center N newton(s)
BBDC before bottom dead center Pa pascal(s)
BDC
BTDC before top dead center psi pound(s) per square inch
°C degree(s) Celsius r revolution
DC direct current rpm revolution(s) perminute
F farad(s) TDC top dead center
°F degree(s) Fahrenheit TIR total indicator reading
ft foot, feet
ggram(s) W watt(s)
h hour(s) Ω ohm(s)
L liter(s)
bottom dead center
PS
V
horsepower
volt(s)
Read OWNER’S MANUAL before operating
Foreword
This manual is designed primarily for use by
trained mechanics in a properly equipped shop.
However, it contains enough detail and basic information to make it useful to the owner who desires to perform his own basic maintenance and
repair work. A basic knowledge of mechanics,
the proper use of tools, and workshop procedures must be understood in order to carry out
maintenance and repair satisfactorily. Whenever the owner has insufficient experience or
doubts as to his ability to do the work, all adjustments, maintenance, and repair should be
carried out only by qualified mechanics.
In order to perform the work efficiently and
to avoid costly mistakes, read the text, thoroughly familiarize yourself with the procedures
before starting work, and then do the work carefully in a clean area. Whenever special tools or
equipment are specified, do not use makeshift
tools or equipment. Precision measurements
can only be made if the proper instruments are
used, and the use of substitute tools may adversely affect safe operation.
To get the longest life out of your motorcycle:
Follow the Periodic Maintenance Chart in the
•
Service Manual.
Be alert for problems and non-scheduled
•
maintenance.
Use proper tools and genuine Kawasaki mo-
•
torcycle parts. Special tools, gauges, and
testers that are necessary when servicing
Kawasaki Motorcycles are introduced by the
Service Manual. Genuine parts provided as
spare parts are listed in the Parts Catalog.
Follow the procedures in this manual care-
•
fully. Don’t take shortcuts.
Remember to keep complete records of main-
•
tenance and repair with dates and any new
parts installed.
How to Use this Manual
In this manual, the product is divided into
its major systems and these systems make up
the manual’s chapters. The Quick Reference
Guide shows you all of the product’s system
and assists in locating their chapters. Each
chapter in turn has its own comprehensive Table of Contents.
For example, if you want ignition coil information, use the Quick Reference Guide to locate
the Electrical System chapter. Then, use the
Table of Contents on the first page of the chapter to find the Ignition Coil section.
Whenever you see these WARNING and
CAUTION symbols, heed their instructions!
Always follow safe operating and maintenance
practices.
WARNING
This warning symbol identifies special
instructions or procedures which, if not
correctly followed, could result in per-
sonal injury, or loss of life.
CAUTION
This caution symbol identifies special
instructions or procedures which, if not
strictly observed, could result in dam-
age to or destruction of equipment.
This manual contains four more symbols (in
addition to WARNING and CAUTION) which will
help you distinguish different types of information.
NOTE
This note symbol indicates points of par-
○
ticular interest for more efficient and con-
venient operation.
Indicates a procedural step or work to be
•
done.
Indicates a procedural sub-step or how to do
○
the work of the procedural step it follows. It
also precedes the text of a NOTE.
Indicates a conditional step or what action to
take based on the results of the test or inspec-
tion in the procedural step or sub-step it fol-
lows.
In most chapters an exploded view illustration
of the system components follows the Table of
Contents. In these illustrations you will find the
instructions indicating which parts require specified tightening torque, oil, grease or a locking
agent during assembly.
GENERAL INFORMATION 1-1
General Information
Table of Contents
Before Servicing ..................................................................................................................... 1-2
Model Identification................................................................................................................. 1-5
General Specifications............................................................................................................ 1-7
Technical Information.............................................................................................................. 1-13
Unit Conversion Table ............................................................................................................ 1-21
1
1-2 GENERAL INFORMATION
Before Servicing
Before starting to perform an inspection service or carry out a disassembly and reassembly operation on a motorcycle, read the precautions given below. To facilitate actual operations, notes, illustrations, photographs, cautions, and detailed descriptions have been included in each chapter wherever
necessary. This section explains the items that require particular attention during the removal and
reinstallation or disassembly and reassembly of general parts.
Especially note the following:
(1) Dirt
Before removal and disassembly, clean the motorcycle. Any dirt entering the engine will shorten
the life of the motorcycle. For the same reason, before installing a new part, clean off any dust or
metal filings.
(2) Battery Ground
Disconnect the ground (–) cable from the battery before performing any disassembly operations
on the motorcycle. This prevents the engine from accidentally turning over while work is being
carried out, sparks from being generated while disconnecting the leads from electrical parts, as
well as damage to the electrical parts themselves. For reinstallation, first connect the positive
cable to the positive (+) terminal of the battery
(3) Installation, Assembly
Generally, installation or assembly is the reverse of removal or disassembly. However, if installation or assembly sequence is given in this Service Manual, follow it. Note parts locations and
cable, wire, and hose routing during removal or disassembly so they can be installed or assembled in the same way. It is preferable to mark and record the locations and routing whenever
possible.
(4) Tightening Sequence
When installing bolts, nuts, or screws for which a tightening sequence is given in this Service
Manual, make sure to follow the sequence. When installing a part with several bolts, nuts, or
screws, start them all in their holes and tighten them to a snug fit, thus ensuring that the part has
been installed in its proper location. Then, tighten them to the specified torque in the tightening
sequence and method indicated. If tightening sequence instructions are not given, tighten them
evenly in a cross pattern. Conversely, to remove a part, first loosen all the bolts, nuts, or screws
that are retaining the part a 1/4-turn before removing them.
(5) Torque
When torque values are given in this Service Manual, use them. Either too little or too much
torque may lead to serious damage. Use a good quality, reliable torque wrench.
(6) Force
Common sense should dictate how much force is necessary in assembly and disassembly. If
a part seems especially difficult to remove or install, stop and examine what may be causing the
problem. Whenever tapping is necessary, tap lightly using a wooden or plastic-faced mallet. Use
an impact driver for screws (particularly for the removing screws held by non-permanent locking
agent) in order to avoid damaging the screw heads.
(7) Edges
Watch for sharp edges, as they could cause injury through careless handling, especially during
major engine disassembly and assembly. Use a clean piece of thick cloth when lifting the engine
or turning it over.
(8) High-Flash Point Solvent
A high-flash point solvent is recommended to reduce fire danger. A commercial solvent commonly available in North America is standard solvent (generic name). Always follow manufacturer
and container directions regarding the use of any solvent.
(9) Gasket, O-ring
Replace a gasket or an O-ring with a new part when disassembling. Remove any foreign matter
from the mating surface of the gasket or O-ring to ensure a perfectly smooth surface to prevent
oil or compression leaks.
(10)Liquid Gasket, Locking Agent
Clean and prepare surfaces where liquid gasket or non-permanent locking agent will be used.
Apply them sparingly. Excessive amount may block engine oil passages and cause serious damage.
GENERAL INFORMATION 1-3
Before Servicing
(11)Press
When using a press or driver to install a part such as a wheel bearing, apply a small amount of
oil to the area where the two parts come in contact to ensure a smooth fit.
(12)Ball Bearing and Needle Bearing
Do not remove a ball bearing or a needle bearing unless it is absolutely necessary. Replace any
ball or needle bearings that were removed with new ones. Install bearings with the manufacturer
and size marks facing out, applying pressure evenly with a suitable driver. Apply force only to the
end of the race that contacts the press fit portion, and press it evenly over the base component.
(13)Oil Seal and Grease Seal
Replace any oil or grease seals that were removed with new ones, as removal generally damages seals. Oil or grease seals should be pressed into place using a suitable driver, applying a
force uniformly to the end of seal until the face of the seal is even with the end of the hole, unless
instructed otherwise. When pressing in an oil or grease seal which has manufacturer’s marks,
press it in with the marks facing out.
(14)Circlip, Retaining Ring, and Cotter Pin
When installing circlips and retaining rings, take care to compress or expand them only enough
to install them and no more. Install the circlip with its chamfered side facing load side as well.
Replace any circlips, retaining rings, and cotter pins that were removed with new ones, as removal weakens and deforms them. If old ones are reused, they could become detached while
the motorcycle is driven, leading to a major problem.
(15)Lubrication
Engine wear is generally at its maximum while the engine is warming up and before all the sliding
surfaces have an adequate lubricative film. During assembly, make sure to apply oil to any sliding
surface or bearing that has been cleaned. Old grease or dirty oil could have lost its lubricative
quality and may contain foreign particles that act as abrasives; therefore, make sure to wipe it off
and apply fresh grease or oil. Some oils and greases in particular should be used only in certain
applications and may be harmful if used in an application for which they are not intended.
(16)Direction of Engine Rotation
To rotate the crankshaft manually, make sure to do so in the direction of positive rotation. Positive rotation is counterclockwise as viewed from the left side of the engine. To carry out proper
adjustment, it is furthermore necessary to rotate the engine in the direction of positive rotation as
well.
(17)Replacement Parts
When there is a replacement instruction, replace these parts with new ones every time they are
removed.
Replacement parts will be damaged or lose their original function once they are removed. Therefore, always replace these parts with new ones every time they are removed. Although the previously mentioned gasket, O-ring, ball bearing, needle bearing, grease seal, oil seal, circlip, and
cotter pin have not been so designated in their respective text, they are replacement parts.
(18)Electrical Leads
All the electrical leads are either one-color or two-color. A two-color lead is identified first by
the primary color and then the stripe color. For example, a yellow lead with thin red stripes is
referred to as a “yellow/red” lead; it would be a “red/yellow” lead if the colors were reversed.
Unless instructed otherwise, electrical leads must be connected to leads of the same color.
Two-Color Electrical
1-4 GENERAL INFORMATION
Before Servicing
(19)Inspection
When parts have been disassembled, visually inspect these parts for the following conditions
or other damage. If there is any doubt as to the condition of them, replace them with new ones.
Abrasion Crack Hardening Warp
Bent Dent Scratch Wear
Color change
(20)Specifications
Specification terms are defined as follows:
“Standards” s how dimensions or performances which brand-new parts or systems have.
“Service Limits” indicate the usable limits. If the measurement shows excessive wear or deteri-
orated performance, replace the damaged parts.
Deterioration
Seizure
Model Identification
KX125-M1 Left Side View
GENERAL INFORMATION 1-5
KX125-M1 Right Side View
1-6 GENERAL INFORMATION
Model Identification
KX250-M1 Left Side View
KX250-M1 Right Side View
GENERAL INFORMATION 1-7
General Specifications
Items KX125-M1 KX125-M2 ∼ M3 KX125M6F ∼
Dimensions
Overall Length 2 155 mm (84.8 in.) 2 165 mm (85.2 in.)
Overall Width 825 mm (32.5 in.) 840 mm (33.1 in.) 815 mm (32.1 in.)
Overall Height 1 200 mm (47.2 in.) 1 265 mm (49.8 in.)
Wheelbase
Road Clearance 340 mm (13.4 in.) ←
Seat Height 930 mm (36.6 in.) 940 mm (37.0 in.)
Dry Mass 87 kg (192 lb) ←
Curb Mass:
Front
Rear
Fuel Tank Capacity 8.2L(2.2USgal) ←
Engine
Type 2-stroke, single cylinder,
Cooling System Liquid-cooled ←
Bore and Stroke 54.0 × 54.5 mm (2.13 × 2.15 in.) ←
Displacement 124 cm³(7.6 cu in.) ←
Compression R atio:
Low Speed
High Speed 8.1 : 1 8.5: 1(EUR)8.3: 1
Carburetion System Carburetor, MIKUNI TMX38χ ←
Starting System Primary kick ←
Ignition System CDI ←
Ignition Timing
Spark Plug NGK BR9EIX NGK R6918B-9 NGK BR9ECMVX
Port Timing
Inlet:
Open Full open ←
Close – –
Scavenging:
Open 64.9° BBDC
Close 64.9° ABDC ←
Exhaust:
Open 73.8° BBDC (low speed),
Close 73.8° ABDC (low speed), ←
Lubrication System
(Gasoline : Oil)
Drive Train
Primary Reduction
System:
Type Gear ←
Reduction Ratio 3.200 (64/20) ←
1 455 mm (57.3 in.) 1 470 mm (57.9 in.)
45 kg (99 lb)
47 kg (104 lb)
crankcase reed valve
10.6 : 1
13° BTDC @9 710 r/min (rpm) 13° BTDC @9 710 r/min (rpm)
95.4° BBDC (high speed) ←
95.4° ABDC (high speed) ←
Petrol mix (32 : 1) ←
11.1 : 1 (EUR) 10.9 : 1
←
←
←
←
←
1-8 GENERAL INFORMATION
General Specifications
Items KX125-M1 KX125-M2 ∼ M3 KX125M6F ∼
Clutch Type Wet, multi disc ←
Transmission:
Type 6-speed, constant mesh, return
shift
Gear Ratios:
1st 2.384 (31/13) ←
2nd
3rd 1.529 (26/17) ←
4th 1.294 (22/17) ←
5th 1.125 (27/24) ←
6th 1.000 (25/25) ←
Final Drive System:
Type
Reduction Ratio 3.923 (51/13) ←
Overall Drive Ratio 12.553 @Top gear ←
Transmission Oil:
Grade API SE, SF or SG
Viscosity SAE 10W-40 ←
Capacity 0.7 L (0.74 US qt) ←
Frame
Type Tubular, semi-double cradle ←
Steering Angle 45° to either side 42° to either side
Caster (rake angle) 27.5° 27°
Trail 100 mm (3.9 in.) 113 mm (4.4 in.)
Front Tire:
Size 80/100-21 51M
Make/Type DUNLOP, Tube type ←
Rear Tire:
Size 100/90-19 57M
Make/Type DUNLOP, Tube type ←
Rim Size:
Front 21 × 1.60 ←
Rear 19 × 1.85 ←
Front Suspension:
Type
Wheel Travel 300 mm (11.8 in.) ←
Rear Suspension:
Type Swingarm (Uni-trak) Swingarm (New Uni-trak)
Wheel Travel 310 mm (12.2 in.) ←
Brake Type:
Front and Rear Single disc ←
1.857 (26/14)
Chain drive
←
API SH or SJ with JASO MA
Telescopic fork (up side down)
←
←
←
API SH, SJ or
SL with JASOMA
(KX125M7F ∼)
←
←
←
GENERAL INFORMATION 1-9
General Specifications
Items KX125-M1 KX125-M2 ∼ M3 KX125M6F ∼
Effective Disc Diameter:
Front
Rear 200 mm (7.9 in.) 215 mm (8.5 in.)
Specifications are subject to change without notice, and may not apply to every country.
(EUR): Europe Model
220 mm (8.7 in.) 225 mm (8.9 in.)
1-10 GENERAL INFORMATION
General Specifications
Items KX250-M1 KX250-M2
Dimensions
Overall Length 2 175 mm (85.6 in.) ←
Overall Width 825 mm (32.5 in.) 840 mm (33.1 in.)
Overall Height 1 205 mm (47.4 in.) 1 265 mm (49.8 in.)
Wheelbase 1 480 mm (58.3 in.) ←
Road Clearance 355 mm (14.0 in.) 340 mm (13.4 in.)
Seat Height 945 mm (37.2 in.)
Dry Mass 97 kg (214 lb) ←
Curb Mass:
Front 50 kg (110 lb) ←
Rear 51 kg (112 lb) ←
Fuel tank Capacity 8.2 L (2.2 US gal) ←
Engine
Type 2-stroke, single cylinder, piston
reed valve
Cooling System
Bore and Stroke 66.4 × 72.0 mm (2.61 × 2.85 in.) ←
Displacement 249 cm³ (15.25 cu in.) ←
Compression Ratio
Low Speed 10.1 : 1 10.5 : 1
High Speed 8.6 : 1 8.8 : 1
Carburetion System Carburetor, KEIHIN PWK38S
Starting System Primary kick ←
Ignition System CDI ←
Ignition Timing 14° BTDC @7 740 r/min (rpm) ←
Spark Plug NGK BR8EIX ←
Port Timing:
Inlet:
Open Full open ←
Close – –
Scavenging:
Open 57.6° BBDC 59.3° BBDC
Close 57.6° ABDC 59.3° ABDC
Exhaust:
Open 78.1° BBDC (low speed), 78.4° BBDC (low speed),
Close 78.1° ABDC (low speed), 78.4° ABDC (low speed),
Lubrication System (Gasoline: Oil) Petrol mix (32 : 1)
Drive Train
Primary Reduction System:
Type Gear ←
Reduction ratio 3.000 (63/21) ←
Clutch Type Wet, multi disc ←
Liquid-cooled ←
91.4° BBDC (high speed) 92.2° BBDC (high speed)
91.4° ABDC (high speed) 92.2° ABDC (high speed)
←
←
←
←
GENERAL INFORMATION 1-11
General Specifications
Items KX250-M1 KX250-M2
Transmission:
Type 5 speed, constant mesh, return
shift
Gear Ratios:
1st
2nd 1.437 (23/16) ←
3rd 1.176 (20/17) ←
4th 1.000 (21/21) ←
5th 0.869 (20/23) ←
Final Drive System
Type
Reduction Ratio 3.769 (49/13) ←
Overall Drive Ratio 9.832 @Top gear ←
Transmission Oil:
Grade API SE, SF or SG ←
Viscosity
Capacity 0.85 L (0.90 US qt) ←
Frame
Type Tubular, semi-double cradle ←
Steering Angle 45° to either side 42° to either side
Caster (rake angle) 27°
Trail
Front Tire:
Size 80/100-21 51M
Make/Type BRIDGESTONE, Tube type
Rear Tire:
Size 110/90-19 62M
Make/Type BRIDGESTONE, Tube type ←
Rim Size:
Front 21 × 1.60 ←
Rear 19 × 2.15 ←
Front Suspension:
Type Telescopic fork (up side down) ←
Wheel Travel 300 mm (11.8 in.) ←
Rear Suspension:
Type Swingarm (Uni-trak) Swingarm (New Uni-trak)
Wheel Travel
Brake Type:
Front and Rear Single disc ←
1.800 (27/15)
Chain drive
API SH or SJ with JASO MA
SAE 10W-40
97 mm (3.8 in.) 112mm(4.4in.)
(EUR) DUNLOP, Tube type ←
(EUR) DUNLOP, Tube type ←
310 mm (12.2 in.)
←
←
←
←
←
←
←
←
←
←
1-12 GENERAL INFORMATION
General Specifications
Items KX250-M1 KX250-M2
Effective Disc Diameter:
Front 220 mm (8.7 in.) 225 mm (8.9 in.)
Rear 200 mm (7.9 in.) 215 mm (8.5 in.)
Specifications are subject to change without notice, and may not apply to every country.
(EUR): Europe Model
GENERAL INFORMATION 1-13
Technical Information
Ratchet-Type Shift Mechanism (KX250M, KX125M)
The shift mechanism of the KX250M (5-speed) is shown in the following figure.
○
This mechanism is stronger and simpler than the usual slide type and enables light and positive
○
shifting. When the shift pedal [D] i s applied, its turning force is transmitted almost directly to the
shift drum [E].
The mechanism has shorter length between the shift drum and the drive shaft, compared with the
○
previous model (for example, from 67 mm to 43.2 mm for KX125).
The shift force is transmitted as follows:
○
Shift Pedal → Shift Shaft [F] → Shift Mechanism Arm [G] → Ratchet [H] → Pawls [I], [M] in Ratchet
→ Shift Drum Cam [J] → Shift Forks → Gears
A. Top View
B. Front
C. Ratchet Plate
D. Shift Pedal
E. Shift Drum
F. To p Vie w
G. Shift Mechanism Arm
H. Ratchet
I. Upper Pawls
J. Shift Drum Cam
K. Gear Set Lever
L. Return Spring Pin
M. Lower Pawl
N. Neutral Detent
O. Return Spring
1-14 GENERAL INFORMATION
Technical Information
This mechanism operates as follows:
○
1. Suppose the 1st gear position is set as shown.
Neutral Detent [N]
2. Shift Up (for example: shift from 1st to 2nd)
(→) : transmitting of shift force
The shift pedal is lifted. → The arm [G] turns counterclockwise until it stops at pin [L]. → ratchet [H] → lower
pawl [M] → shift drum cam [J] → shift drum → The gear
is shifted in 2nd position.
3. Ratchet Returns.
The arm [G] returns by force of spring [O]. → The ratchet
[H] disengages to be free by itself. → The set lever [K]
holds the shift drum cam [J]. → The ratchet [H] returns
(turns clockwise).
4. The 2nd Gear Position settles.
The upper and lower pawls [I], [M] catch the next teeth
inside the shift drum cam [J] → The ratchet [H] settles in
position. → The 2nd gear position settles.
5. Shift Down (for example: shift from 2nd to 1st)
The shift pedal is depressed. → The arm [G] turns clockwise until it stops at the pin [L]. → ratchet [H] → upper
pawl [I] → shift drum cam [J] → shift drum → The gear is
shifted into 1st position. → (continues to operate in the
samewayasShiftUp)
GENERAL INFORMATION 1-15
Technical Information
Chrome Composite Plating Cylinder (KX250M, KX125M)
This new cylinder bore [A] has Kawasaki’s compos-
○
ite cylinder plating, which is used for the first time on
two stroke engines. The composite plating includes a
nickel-phosphorous alloy, inorganic materials like ceramic, silicone carbide and some organic materials.
The treatment improves heat transfer of the cylinder for
○
consistent power output, allows closer piston-to-cylinder
clearances for more horsepower.
The treatment is porous, so it holds lubrication well, and
○
hard, so it resists abrasion and seizure.
This plating gets on well even the chamfered edge of the
○
cylinder top or port.
This improves the surface of the chamber at the top of
○
the cylinder, preventing hot spots, resultant pre-ignition
and other abnormal combustion in the chamber.
Previous Cylinder [A]
New Cylinder [B]
Exhaust Port [C]
Cylinder Top [D]
This enables the top end of the exhaust port from round
○
to straight in order to ma
mid-high performance and extending piston ring life.
Previous Cylinder [A]
New Cylinder [B]
Exhaust Port [C]
ke gas flow smooth and improve
1-16 GENERAL INFORMATION
Technical Information
KIPS (Kawasaki Integrated Power Valve System, KX250M , KX125M)
KIPS varies the exhaust port height to broaden the useful rpm range for low end and mid-range
○
without sacrificing the top end power (see ’95 KDX200H Service Manual (Part No. 99924-1181-01)
for basic information about KIPS).
KIPS is 2-stage-3-way type: the main exhaust port is opened earlier than the sub-exhaust ports
○
(2-stage) and they are opened differently in low, middle and high rpm (3-way).
(In low rpm)
resonator: open to fully, sub-exhaust ports and main exhaust port: close
(In middle rpm)
resonator: close, main exhaust port: open to fully, sub-exhaust ports open to halfway
(Inhighrpm)
resonator: close, main exhaust port and sub-exhaust ports open fully.
The KIPS valve is now made of aluminum instead of steel to save weight.
○
The KIPS main valve holder shape is modified to match the straightened exhaust port, and timing
○
for the main and sub-valves is changed to deliver more power in the low to mid-range.
The main valve end is changed from thick end to thin end, reducing exhaust pressure on the valve
○
and making valve operation smooth.
(KX250M)
A. Previous KIPS
B. New KIPS
Technical Information
(KX125M)
GENERAL INFORMATION 1-17
A. Previous KIPS
B. New Model
C. Full Opened Position
D. Low Speed Position
E. Straightened Exhaust Passage
The KIPS governor is modified so that the exhaust valves
○
operate over a wider rpm range to improve low and mid
-range power and smooth the power delivery.
The KX250’s governor inside is changed from straight to
○
concave in order to move the balls smoothly.
Previous Governor [A]
New Governor [B]
Carburetor (KX250M)
The 38.7 mm (1.524 in.) Keihin PWK 38S carburetor
○
helps boost mid-range and top-end power.
1-18 GENERAL INFORMATION
Technical Information
The crescent shaped slide [A] enables the needle to sit
○
closer to the intake ports for quicker throttle response.
Large bores in the front and back of the carburetor and
○
a smoother shape (38 to 40 mm-tapered bore [B]) boost
mixture flow for more mid-range and top-end power.
The semi air bleed needle jet [C] improves throttle re-
○
sponse in the very low and low range.
Front [D]
The air baffle forms vacuum, the stop narrows the outlet and speeds up outflow from the needle jet,
○
improving atomization.
←—: Fuel Droplets
← - -: Fuel Mist
A. Previous Carburetor
B. New Carburetor
C. Jet Needle
D. Air Baffle
The new main air inlet tends to take in static pressure and to exclude dynamic pressure and vor-
○
texes, making the main air flow stable.
E. Needle Jet
F. S t o p
G. Engine Inlet
H. Main Air
Technical Information
A. Previous Carburetor
B. New Carburetor
C. Jet Needle
D. Air Baffle
E. Main Air
F. Needle Jet
G. Engine Inlet
GENERAL INFORMATION 1-19
Carburetor (KX125M)
The 38 mm (1.496 in.) Mikuni TMX 38-27 carburetor
○
helps boost mid-range and top-end power.
The arched slide [A] improves throttle response in the very
○
low and low ranges.
Large bores in the front and back of the carburetor and
○
a smoother shape (38 to 40 mm-tapered bore [B]) boost
mixture flow for more mid-range and top-end power.
The semi air bleed needle jet [C] improves throttle re-
○
sponse in the low range and provides proper mixture from
the low to top range.
Front [D]
1-20 GENERAL INFORMATION
Technical Information
In low range, fuel drops in the fuel/air mixture is larger and tends to stick to the carburetor wall.
○
The arched slide deflects fuel/air mixture flow from the wall to the middle of the carburetor for better
atomization and better throttle response.
A. Previous Carburetor
B. New Carburetor
C. Flat Slide (piston valve)
D. Arched Shape Slide (piston valve)
E. Engine Intake
The semi air bleed hole is positioned at the side of the needle jet, where fuel mixes with air well (due
○
to enough fuel and faster air flow than in main bore), resulting in better atomizing. The air screen
suppresses dynamic pressure around the main air inlet.
A. Previous Carburetor
B. New Carburetor
C. Jet Needle
D. Air Baffle
E. Main Air
F. Needle Jet
G. Engine Intake
H. Semi Air Bleed Hole
I. Air Screen
Unit Conversion Table
GENERAL INFORMATION 1-21
Prefixes for Units:
Prefix Symbol Power
mega M × 1 000 000
kilo k ×1000
centi c ×0.01
milli m × 0.001
micro µ × 0.000001
Units of Mass:
kg ×2.205=lb
g × 0.03527 = oz
Units of Volume:
L × 0.2642 =
L × 0.2200 = gal (imp)
L × 1.057 = qt (US)
L × 0.8799 = qt (imp)
L × 2.113 = pint (US)
L × 1.816 =
mL × 0.03381 =
mL × 0.02816 = oz (imp)
mL × 0.06102 = cu in
gal (US)
pint (imp)
oz (US)
Units of Length:
km × 0.6214 = mile
m × 3.281 = ft
mm × 0.03937 = in
Units of Torque:
N·m × 0.1020 = kgf·m
N·m × 0.7376 = ft·lb
N·m × 8.851 = in·lb
kgf·m × 9.807 = N·m
kgf·m × 7.233 = ft·lb
kgf·m × 86.80 = in·lb
Units of Pressure:
kPa × 0.01020 = kgf/cm²
kPa × 0.1450 = psi
kPa × 0.7501 = cm Hg
kgf/cm² × 98.07 = kPa
kgf/cm²
cmHg×1.333=kPa
× 14.22 = psi
Units of Speed:
km/h
× 0.6214 = mph
Units of Force:
N × 0.1020 = kgf
N × 0.2248 = lb
kgf × 9.807 = N
kgf × 2.205 = lb
Units of Temperature:
Units of Power:
kW ×1.360=PS
kW ×1.341=HP
PS × 0.7355 = kW
PS × 0.9863 = HP
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