KYMCO Mongoose/KXR 250, Mongoose 250, KXR 250 Service Manual

PREFACE

This Service Manual describes the
technical features and servicing
procedures for the KYMCO
Mongoose/KXR 250.

Section 1 contains the precautions for
all operations stated in this manual.
Read them carefully before starting any
operation.

Section 2 is the removal/installation
procedures for the frame covers which
are subject to higher removal/installation
frequency during maintenance and
servicing operations.

Section 3 describes the inspection/
adjustment procedures, safety rules and
service information for each part,
starting from periodic maintenance.

Sections 4 through 19 give instructions
for disassembly, assembly and
inspection of engine, chassis frame and
electrical equipment.

Most sections start with an assembly or
system illustration and troubleshooting
for the section. The subsequent pages
give detailed procedures for the section.

KWANG YANG MOTOR CO., LTD.

OVERSEAS SALES DEPARTMENT

OVERSEAS SERVICE SECTION

TABLE OF CONTENTS

GENERAL INFORMATION 1
FRAME COVERS/EXHAUST MUFFLER 2
INSPECTION/ADJUSTMENT 3
LUBRICATION SYSTEM 4
FUEL SYSTEM 5

ENGINE REMOVAL 6
CYLINDER HEAD/VALVES 7
CYLINDER/PISTON 8
DRIVE AND DRIVEN PULLEYS

9

FINAL REDUCTION/TRANSMISSION
SYSTEM

10

CRANKCASE/CRANKSHAFT/
BALANCE SHAFT

11

COOLING SYSTEM

12

BRAKE SYSTEM

13

FRONT WHEEL/FRONT
SUSPENSION/STEERING SYSTEM

14

REAR WHEEL/AXLE/SUSPENSION

15

BATTERY/CHARGING SYSTEM/A.C.
GENERATOR

16

IGNITION SYSTEM 17
STARTING SYSTEM 18
BULBSREMOVAL/INSTRUMENT/

HORN

19

The information and contents include

d

in this manual may be different from
the motorcycle in case specifications
are changed.

CHASSIS

ELECTRICAL

EQUIPMENT

ENGINE

1. GENERAL INFORMATION

1-0

Mongoose/KXR 250

1

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

GENERAL INFORMATION

__________________________________________________________________________________

SERIAL NUMBER---------------------------------------------------------- 1- 1
SPECIFICATIONS---------------------------------------------------------- 1- 2
SERVICE PRECAUTIONS------------------------------------------------ 1- 3
TORQUE VALUES --------------------------------------------------------- 1-11
SPECIAL TOOLS ----------------------------------------------------------- 1-12
LUBRICATION POINTS -------------------------------------------------- 1-13
CABLE & HARNESS ROUTING ---------------------------------------- 1-16
WIRING DIAGRAM-------------------------------------------------------- 1-19
TROUBLESHOOTING----------------------------------------------------- 1-21

1

1. GENERAL INFORMATION

1-1

Mongoose/KXR 250

SERIAL NUMBER

Location of Engine Serial Numbe

r

Location of Frame Serial Numbe

r

1. GENERAL INFORMATION

1-2

Mongoose/KXR 250

SPECIFICATIONS

Name & Model No. LA50AA/AB
Motorcycle Name & Type Mongoose/KXR
Overall length (mm) 1700
Overall width (mm) 1070
Overall height (mm) 1080
Wheel base (mm) 1180
Engine type O.H.C.
Displacement (cc) 249
Fuel Used 92# nonleaded gasoline

Front wheel 93.1

Net weight (kg) Rear wheel 84.9

Total 178

Front wheel 100

Gross weight(kg) Rear wheel 91

Total 191

Front wheel 21*7-10

Rear wheel 20*11-9

Ground clearance (mm) 130
Perform-

Breakin

g

distance

(m)(30KPH)

29.27 below

ance

Min. turning radius (m) 2.865

Starting system

Starting motor

Type Gasoline, 4-stroke
Cylinder arrangement Single cylinder
Combustion chamber type Semi-sphere
Valve arrangement O.H.C., chain drive
Bore x stroke (mm) 72.7 x 60
Compression ratio 10.3:1

Compression pressure
(kg/cm²)

15.0

Max. output (ps/rpm) 17/7000
Max. torque (kg m/rpm) 2.0/5500

Intake

Open 8.1° BTDC

Port

(1mm)

Close 41° ABDC

timin

g

Exhaust

Open 37° BBDC

(1mm)

Close 7.9° ATDC

Valve clearance

Intake 0.1

(cold) (mm)

Exhaust 0.1

Idle speed (rpm) 1500rpm

Lubrication type

Forced

p

ressure &

Wet sump
Oil pump type Inner/outer rotor type
Oil filter type Full-flow filtration
Oil capacity 1.6 liter
Oil exchanging
capacity

1.4 liter

Cooling Type Water cooling

Air cleaner type & No Sponge
Fuel capacity 13 liters

Type PD
Float lever 14.8mm
Venturi dia.(mm) φ22
Throttle type PISTON
Type CDI
Ignition timing 5°BTDC/2000rpm
Contact breaker Non-contact point type

Spark plug DPR7EA-9

Spark plug gap 0.6～0.7mm
Battery Capacity 12V12AH
Clutch Type CVT

Type Helical gear/spur gear
Operation

Automatic centrifugal

Type
Type Chain drive
Reduction 1st

24.7

ratio

2nd

9.33

Reverse ratio

47.4

FR/RR tire rolling
circumference(mm)

1675/1596

Tire pressure

Fron

t

0.28

(kg/cm²)

Rear 0.28

Turning Left 40°
angle

Right 40°

Brake syste

m

Rea

r

Disk brake

type

Front Disk brake
Front

Double wishbone

Suspension
type

Rear

Link suspension

Frame type Steel tube frame

Tires

Engine

Lubrication

S

y

stem

Fuel S

y

stem

Carbureto

r

Electrical Equipment

I

g

nition S

y

stem

Power Drive System

Transmis-

sion Gear

Reduction

Gear

Moving Device

Damping

Device

1. GENERAL INFORMATION

1-3

Mongoose/KXR 250

SERVICE PRECAUTIONS

 Make sure to install new gaskets, O-rings,

circlips, cotter pins, etc. when
reassembling.

 When tightening bolts or nuts, begin with

larger-diameter to smaller ones at several
times, and tighten to the specified torque
diagonally.

 Use genuine parts and lubricants.

 When servicing the motorcycle, be sure

to use special tools for removal and
installation.

 After disassembly, clean removed parts.

Lubricate sliding surfaces with engine oil
before reassembly.

1. GENERAL INFORMATION

1-4

Mongoose/KXR 250

 Apply or add designated greases and

lubricants to the specified lubrication
points.

 After reassembly, check all parts for

proper tightening and operation.

 When two persons work together, pay

attention to the mutual working safety.

 Disconnect the battery negative (-)

terminal before operation.

 When using a spanner or other tools,

make sure not to damage the motorcycle
surface.

 After operation, check all connecting

points, fasteners, and lines for proper
connection and installation.

 When connecting the battery, the positive

(+) terminal must be connected first.

 After connection, apply grease to the

battery terminals.

 Terminal caps shall be installed securely.

1. GENERAL INFORMATION

1-5

Mongoose/KXR 250

 If the fuse is burned out, find the cause

and repair it. Replace it with a new one
according to the specified capacity.

 After operation, terminal caps shall be

installed securely.

 When taking out the connector, the lock

on the connector shall be released before
operation.

 Hold the connector body when

connecting or disconnecting it.

 Do not pull the connector wire.

 Check if any connector terminal is

bending, protruding or loose.

Confir

m

Capacity

1. GENERAL INFORMATION

1-6

Mongoose/KXR 250

 The connector shall be inserted

completely.

 If the double connector has a lock,

lock it at the correct position.

 Check if there is any loose wire.

 Before connecting a terminal, check

for damaged terminal cover or loose
negative terminal.

 Check the double connector cover for

proper coverage and installation.

 Insert the terminal completely.
 Check the terminal cover for proper

coverage.

 Do not make the terminal cover opening

face up.

 Secure wire harnesses to the frame with

their respective wire bands at the
designated locations.
Tighten the bands so that only the
insulated surfaces contact the wire
harnesses.

Snapping!

1. GENERAL INFORMATION

1-7

Mongoose/KXR 250

 After clamping, check each wire to make

sure it is secure.

 Do not squeeze wires against the weld or

its clamp.

 After clamping, check each harness to

make sure that it is not interfering with
any moving or sliding parts.

 When fixing the wire harnesses, do not

make it contact the parts which will
generate high heat.

 Route wire harnesses to avoid sharp

edges or corners. Avoid the projected
ends of bolts and screws.

 Route wire harnesses passing through the

side of bolts and screws. Avoid the
projected ends of bolts and screws.

N

o Contact !

1. GENERAL INFORMATION

1-8

Mongoose/KXR 250

 Route harnesses so they are neither

pulled tight nor have excessive slack.

 Protect wires and harnesses with

electrical tape or tube if they contact a
sharp edge or corner.

 When rubber protecting cover is used to

protect the wire harnesses, it shall be
installed securely.

 Do not break the sheath of wire.
 If a wire or harness is with a broken

sheath, repair by wrapping it with
protective tape or replace it.

 When installing other parts, do not press

or squeeze the wires.

Do not pull
too ti

g

ht!

Do not press
or squeeze
the wire.

1. GENERAL INFORMATION

1-9

Mongoose/KXR 250

 After routing, check that the wire

harnesses are not twisted or kinked.

 Wire harnesses routed along with

handlebar should not be pulled tight, have
excessive slack or interfere with adjacent
or surrounding parts in all steering
positions.

 When a testing device is used, make sure

to understand the operating methods
thoroughly and operate according to the
operating instructions.

 Be careful not to drop any parts.

 When rust is found on a terminal, remove

the rust with sand paper or equivalent
before connecting.

Do you understand
the instrument? Is
the instrument set
correctly?

Remove Rust !

1. GENERAL INFORMATION

1-10

Mongoose/KXR 250

 Symbols:

The following symbols represent the
servicing methods and cautions included
in this service manual.

: Apply engine oil to the

specified points. (Use
designated engine oil for
lubrication.)

: Apply grease for

lubrication.

: Transmission Gear Oil

(90#)

: Use special tool.

: Caution

: Warning

Engine Oil

Grease

Gear Oil

Special

1. GENERAL INFORMATION

1-11

Mongoose/KXR 250

TORQUE VALUES

STANDARD TORQUE VALUES

Ite

m

Torque (kgf-m

)

Ite

m

Torque (kgf-m

)

5mm bolt and nut
6mm bolt and nut

8mm bolt and nut
10mm bolt and nut
12mm bolt and nut

14mm bolt and nut

0.45～0.6

0.8～1.2

1.8～2.5

3.0～4.0

5.0～6.0

6.0～8.0

4mm screw
5mm screw

6mm screw, SH bolt
6mm flange bolt and nut
8mm flange bolt and nut
10mm flange bolt and nut

0.2～0.4

0.35～0.5

0.7～1.1

1.0～1.4

2.4～3.0

3.5～4.5

Torque specifications listed below are for important fasteners.

ENGINE

Item Q‘ty Thread dia.(mm) Torque (kgf-m) Remarks

Stud bolt
Oil filter screen cap
Seat ball stopper bolt
L cover
Cam shaft holder
Tappet ADJ nut
Pivot tensioner bolt
Lifter tensioner bolt
Lifter tensioner cap
Mission case bolt
Mission fill bolt
Driver face nut
Clutch outer nut
Drive plate nut
Oneway clutch bolt
ACG flywheel nut
Spark plug
Water pump impeller
Drain plug
Oil pump screw
Head CYL stud bolt (IN pipe)
Head CYL stud bolt (EX pipe)
A.C.G Startor

4
1
1

10

4
2
1
2
1
9
1
1
1
1
3
1
1
1
1
1
2
2
3

8
30
14

6

8

5

8

6

6

8
12
14
12
28

8
14
12

7
12

3

6

8

5

0.7～1.1

1.0～2.0

4.5～5.0

1.0～1.4

2.3～2.7

0.7～1.1

0.8～1.2

1.0～1.4

0.35～0.5

2.4～3.0

2.0～3.0

9.0～10.0

5.0～6.0

5.0～6.0

1.8～2.2

5.5～6.5

1.5～2.0

1.0～1.4

2.0～3.0

0.1～0.3

0.7～1.1

0.7～1.1

0.8～1.0

Apply oil
Apply oil

Apply oil

Apply thread
lock

1. GENERAL INFORMATION

1-12

Mongoose/KXR 250

FRAME

Item Q‘ty Thread dia.(mm) Torque (kgf-m) Remarks

Steering stem nut
Front swing arm nut
Front wheel nut
Rear wheel nut
Front wheel hub nut
Rear wheel hub nut
Front shock absorber upper mount bolt
Front shock absorber lower mount bolt
Rear shock absorber upper mount bolt
Rear shock absorber lower mount bolt
Rear swing arm axle
Rear hub nut
Rear wheel shaft nut
Rear engine bracket upper bolt
Rear engine bracket lower bolt
Engine hanger bracket bolt
Exhaust muffler lock bolt (frame)
Exhaust muffler lock nut (engine)
Rod-end nut

1
8
8
8
2
2
2
2
1
1
1
2
2
1
1
1
2
2
4

14
10
12
12
14
16
10
10
10
10
14
10
40
10
10
10

8
8
8

6.0～8.0

4.0～5.0

4.0～5.0

4.0～5.0

6.0～8.0

9.0～11.0

3.5～4.5

3.5～4.5

3.5～4.5

3.5～4.5

6.0～8.0

3.5～4.5

11.0～13.0

3.5～4.5

3.5～4.5

3.5～4.5

3.2～3.8

1.8～2.2

2.5～3.5

SPECIAL TOOLS

Tool Name Tool No. Remarks Ref. Page

Flywheel puller E003
Valve adjuster E012
Valve spring compressor E040
Oil seal and bearing install E014
Universal holder E017
Flywheel holder E021
Clutch spring compressor E034
Bearing puller E037
Nut wrench F010

1. GENERAL INFORMATION

1-13

Mongoose/KXR 250

LUBRICATION POINTS

ENGINE

Lubrication Points Lubricant

Valve guide/valve stem movable part
Cam lobes
Valve rocker arm friction surface
Cam chain
Cylinder lock bolt and nut
Piston surroundings and piston ring grooves
Piston pin surroundings
Cylinder inside wall
Connecting rod/piston pin hole
Connecting rod big end
Crankshaft right side oil seal
Crankshaft one-way clutch movable part
Oil pump drive chain
Balance gear
A.C. generator
Starter one-way clutch
Bearing movable part
O-ring face
Oil seal lip

•Genuine KYMCO Engine Oil (SAE15W -40)

•API SG Engine Oil

Transmission gear and movable parts Gear oil: SAE90#

1. GENERAL INFORMATION

1-14

Mongoose/KXR 250

FRAME

The following is the lubrication points for the frame.
Use general purpose grease for parts not listed.
Apply clean engine oil or grease to cables and movable parts not specified. This will avoid
abnormal noise and rise the durability of the ATV.

Steering Column Uppe

r

Throttle Cable

Steering Column Lowe

r

Front Swing Arm Bush

Front Swing Ar

m

1. GENERAL INFORMATION

1-15

Mongoose/KXR 250

Sprocket hub/Rea

r

Axle Hub Collar/Oil
Seal/Bearing

Driven Sprocket

Rear Swing Ar

m

Axle

1. GENERAL INFORMATION

1-16

Mongoose/KXR 250

CABLE & HARNESS ROUTING

Headlight Wire

Pilot Lamp Wire

Handlebar Switch Wire

Ignition Switch Wire

Rear Brake Fluid Hose

Harness Wire

Motor Fan Cor

d

Thermostatic Switch Wire

Left Front Brake Fluid Hose

Right Front Brake Fluid Hose

Thermostatic Sensor Wire

Front Brake Fluid Hose

Stop Switch Cor

d

Throttle Cable

1. GENERAL INFORMATION

1-17

Mongoose/KXR 250

Air Vent Tube

Coolant Reservoi

r

Breather Hose

Outlet Water Hose

Temperature Sensor Wire

Inlet Water Hose

Water Hose

Carburetor Drain Tube

Start Motor Cable

Radiator Overflow Tube

A.C.G Cor

d

REG.REC Cor

d

Tail Light Cor

d

Stop Switch Cor

d

1. GENERAL INFORMATION

1-18

Mongoose/KXR 250

Motor Fan Cor

d

Handlebar Switch Cor

d

Rear Brake Fluid Hose

Harness Wire

Blow By Hose

Rear Brake Fluid Hose

Start Motor Cable

Battery Cable

Crankcase Breather Hose

Rear Brake Fluid Hose

1. GENERAL INFORMATION

1-19

Mongoose/KXR 250

WIRING DIAGRAM (OFF ROAD)

1. GENERAL INFORMATION

1-20

Mongoose/KXR 250

WIRING DIAGRAM (ON ROAD)

1. GENERAL INFORMATION

1-21

Mongoose/KXR 250

TROUBLESHOOTING

ENGINE WILL NOT START OR IS HARD TO START

Empty fuel tank
Clogged fuel line between fuel
tank and carburetor
Clogged float oil passage
Clogged fuel tank cap breather
hole
Clogged fuel filter
Clogged fuel valve passage

Faulty spark plug
Fouled spark plug
Faulty ignition unit
Faulty change gear control unit
Faulty pulser coil
Broken or shorted ignition coil
Broken or shorted exciter coil
Faulty ignition switch
Weak or dead battery

Faulty starter clutch
Valve clearance too small
Valve stuck open
Worn cylinder, piston and piston
rings
Leaking cylinder head gasket

Air leaking through intake pipe
Leaking intake manifold
Incorrect ignition timing
Incorrectly adjusted air screw

Flooded carburetor
Clogged air cleaner
Throttle valve excessively open

Check if fuel reaches
carburetor by loosening
drain screw

Remove spark plug and
install it into spark plug
cap to test spark by
connecting it to engine
ground

Inspection/Adjustment

Probable Cause

Spark jumps

Normal

compression

Engine does no

t

fire

Weak or no spark

Low or no

compression

Engine fires bu

t

does not start

Test cylinde

r

compression

Start engine by follow­ing normal starting

p

rocedure

Remove spark plug and
inspect again

Symptom

Fuel reaches

carburetor

Fuel does no

t

reach carburetor

Wet spark plug

Dry spark plug

1. GENERAL INFORMATION

1-22

Mongoose/KXR 250

ENGINE LACKS POWER

Clogged air cleaner
Restricted fuel flow
Clogged fuel tank cap breather hole
Clogged exhaust muffler
Carburetor fuel level too low

Faulty ignition unit
Faulty pulser coil

Improper valve clearance
adjustment
Excessively worn valve seat
(protruded valve stem)

Improper valve and seat contact
Worn cylinder and piston rings
Leaking cylinder head gasket
Improper valve timing

Clean and unclog

Fouled spark plug
Incorrect heat range plug

Oil level too high
Oil level too low
Oil not changed

Clogged oil line
Faulty oil pump

Coolant level too low
Worn cylinder and piston rings
Mixture too lean
Poor quality fuel
Excessive carbon build-up in
combustion chamber
Ignition timing too early

Excessive carbon build-up in
combustion chamber
Poor quality fuel
Clutch slipping
Mixture too lean
Ignition timing too early

Start engine and
accelerate lightly for

Inspection/Adjustment

Symptom

Probable Cause

Engine speed

Correct timin

g

Engine speed does no

t

increase sufficientl

y

Incorrect timin

g

Check ignition timing
(using a timing light)

Test cylinder compression

Check carburetor fo

r

clogging

Rapidly accelerate or run
at hi

g

h speed

Remove spark plug and
inspec

t

Check if engine overheats

Check valve clearance

Correc

t

Incorrec

t

N

ormal

com

p

ression

Abnormal

compression

Remove oil dipstick and
check oil level and condition

Remove cylinder head oil

pip

e bolt and inspec

t

Engine overheats

Engine does no

t

overheats

Plug not fouled o

r

discolored

Plug fouled o

r

discolored

Correct and no

t

contaminated

Incorrect o

r

contaminated

Valve train lubricated

prop

erl

y

Valve train no

t

lubricated properl

y

Engine does not knock

Engine knocks

Not clogged

Clogged

1. GENERAL INFORMATION

1-23

Mongoose/KXR 250

POOR PERFORMANCE (ESPECIALLY AT IDLE AND LOW SPEEDS)

Faulty ignition unit
Faulty pulser coil

Mixture too rich (turn screw
out)
Mixture too lean (turn screw in)

Deteriorated O-ring
Carburetor not securely
tightened
Damaged insulator rubber

Faulty or fouled spark plug
Faulty ignition unit
Faulty A.C. generator
Faulty ignition coil
Broken or shorted spark plug
wire
Faulty ignition switch

Remove spark plug and
install it into spark plug
cap to test spark by
connecting it to engine

g

round

Inspection/Adjustment Symptom Probable Cause

Check ignition timing

Check carburetor gaske

t

for air leaks

Check carburetor ai

r

screw adjustment

Correct timing

Incorrect timing

Correctly adjusted

No air leak

Air leaks

Good spark

Weak or inter-

mittent spark

Incorrectly adjusted

1. GENERAL INFORMATION

1-24

Mongoose/KXR 250

POOR PERFORMANCE (AT HIGH SPEED)

Faulty ignition unit
Faulty pulser coil

Improperly adjusted valve
clearance
Worn valve seat

Empty fuel tank
Clogged fuel tube or filter

Clogged Fuel tank cap breather
hole

Clean and unclog

Cam timing gear aligning marks
not aligned

Faulty spring

Inspection/Adjustment Symptom Probable Cause

Check ignition timing

Check carburetor jets
for clogging

Check fuel pump fo

r

fuel supply

Correct timing

Incorrect timing

Check valve spring
tension

Check valve clearance

Fuel flows freely

Fuel flow restricted

Correc

t

Incorrec

t

Not clogged

Clogged

Correctly adjusted

Incorrectly adjusted

Not weakened

Weak spring

Check valve timing

1. GENERAL INFORMATION

1-25

Mongoose/KXR 250

POOR CHARGING (BATTERY OVER DISCHARGING OR OVERCHARGING)
Undercharging

Dead battery
Faulty battery

Faulty A.C. generator coil
Broken yellow wire
Shorted pink and yellow
wires

Broken red wire

Faulty regulator/rectifier
Poorly connected coupler

Faulty A.C. generator

Overcharging

Broken green wire

Poorly connected coupler

Faulty regulator/rectifier

Start engine and tes

t

limit voltage of battery
terminals

Connect battery (+) wire
to regulator/rectifier
coupler red wire and
battery (-) wire to engine

g

round and test voltage

Inspection/Adjustment

Inspection/Adjustment

Symptom

Symptom

Probable Cause

Probable Cause

Normal voltage

B

attery has voltage
with ignition
switch “ON”

Normal

Voltage does no

t

B

attery has no
voltage with ignition
switc

h

“ON”

Resistance too high

Normal voltage No voltage

Measure resistance
between AC generator
coil terminals

Normal

Abnormal

Check regulator/rectifier
coupler for loose
connection

Normal

Abnormal

Connect battery (+) wire
to regulator/rectifier
coupler green wire and
battery (-) wire to engine

g

round and test voltage

Check regulator/rectifier
coupler for loose
connection

1. GENERAL INFORMATION

1-26

Mongoose/KXR 250

NO SPARK AT SPARK PLUG

Faulty spark plug

Loose spark plug cap

Poorly connected coupler

Faulty ignition switch
Weak battery
Faulty pulser coil
Faulty ignition coil
Faulty charging system

Broken wire harness
Poorly connected coupler

Faulty ignition unit
Faulty change gear control
unit

Faulty ignition coil

Replace with a new
spark plug and inspect
a

g

ain

Check ignition unit
coupler for looseness

Inspection/Adjustment Symptom

Probable Cause

Normal

Abnormal

Normal

Abnormal

Normal

Abnormal

Abnormal

Measure resistance
between terminals of
i

g

nition unit couple

r

Check related parts

Check ignition coil with
a ignition unit tester

Weak or no spark

Not loose

Good spark

Loose

Good

Good

Check spark plug cap
and high-tension wire
for looseness

Check ignition unit
with a ignition unit
teste

r

2. FRAME COVERS/EXHAUST MUFFLER

2-0

Mongoose/KXR 250

2

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

FRAME COVERS/EXHAUST MUFFLER

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 2- 2
TROUBLESHOOTING----------------------------------------------------- 2- 2
FRAME COVERS----------------------------------------------------------- 2- 3
EXHAUST MUFFLER REMOVAL-------------------------------------- 2- 7

2

2. FRAME COVERS/EXHAUST MUFFLER

2-1

Mongoose/KXR 250

2. FRAME COVERS/EXHAUST MUFFLER

2-2

Mongoose/KXR 250

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• When removing frame covers, use special care not to pull them by force because the cover joint
claws may be damaged.

• Make sure to route cables and harnesses according to the Cable & Harness Routing.

TORQUE VALUES

Exhaust muffler lock bolt 3.2～3.8kgf-m
Exhaust muffler lock nut 1.8～2.2kgf-m

TROUBLESHOOTING

Noisy exhaust muffler

• Damaged exhaust muffler

• Exhaust muffler joint air leaks

Lack of power

• Caved exhaust muffler

• Exhaust muffler air leaks

• Clogged exhaust muffler

2. FRAME COVERS/EXHAUST MUFFLER

2-3

Mongoose/KXR 250

FRAME COVERS

SEAT REMOVAL

Pull the lever right and pull up the seat at
the rear.
Remove the seat.

LEFT/RIGHT FRAME COVER
REMOVAL

Remove the seat. (See page 2-3)
Remove the screw and two bolts at the left

frame cover, then remove left frame cover.

Remove the screw and two bolts at the right
frame cover, then remove right frame cover.

REAR FENDER REMOVAL

Remove seat. (See page 2-3)
Remove right and left frame cover. (See
page 2-3)
Remove battery. (See page 16-4)

Remove the fuse box.
Remove the screw attaching the ignition
unit/change gear control unit/starter relay
holder and remove holder.

Sea

t

Frame LeftCove

r

Bolts

Screw

Battery

Bolts

During removal, do not pull the joint
claws forcedly to avoid damage.

＊

Leve

r

Screw

Frame RightCove

r

Screw and Holde

r

Fuse Box

2. FRAME COVERS/EXHAUST MUFFLER

2-4

Mongoose/KXR 250

Remove the three bolts at the rear fender.

Remove the two screws attaching the right
and left floor board.

Remove the two screws attaching the frame
body and three screws attaching the outlet
hose, then remove the rear fender.

HANDLEBAR COVER REMOVAL

Remove the two screws at the handlebar
cover.
Disconnect the indicator lamp coupler, then
remove the handlebar cover.

Bolts

Screws

Screws

Screws

Screws

During removal, do not pull the joint
claws forcedly to avoid damage.

＊

Outlet Hose

Indicator Lamp couple

r

2. FRAME COVERS/EXHAUST MUFFLER

2-5

Mongoose/KXR 250

CENTER FRAME COVER REMOVAL

Remove the seat. (See page 2-3)
Remove the fuel fill cap.

Remove the four bolts at the center frame
cover, then remove the center frame cover.

FRONT FENDER REMOVAL

Remove the seat (See page 2-3), right and
left side frame cover (See page 2-3) and
center frame cover. (See page 2-5)

Remove the two bolts at the front fender left
side.

Remove the two screws attaching the inlet
hose.

Remove the two bolts at the front fender
right side.

Remove the screw, then remove the drive
select grip from the drive select lever.

Bolts

Bolts

Select Grip

Bolts

Screw

Screws

After remove, be sure to tighten the fuel
fill cap.

＊

Fuel Fill Cap

2. FRAME COVERS/EXHAUST MUFFLER

2-6

Mongoose/KXR 250

Disconnect headlight and ignition switch
couplers, then remove the front fender.

RIGHT AND LEFT FLOOR BOARD
REMOVAL

Remove the four screws at the floor board,
then remove the floor board.

FRONT CARRIER REMOVAL

Remove the four bolts at the front carrier,
then remove the front carrier.

Ignition Couple

r

Headlight Couple

r

Screws

Bolts

2. FRAME COVERS/EXHAUST MUFFLER

2-7

Mongoose/KXR 250

EXHAUST MUFFLER

REMOVAL

Remove the two exhaust pipe joint lock
nuts.

Remove the bolt at the exhaust muffler,
disconnect the exhaust pipe from the
exhaust muffler.

Inspect the gasket.
If the exhaust gas leaks, the gasket should

be replaced.

Install by reversing the removal sequence.

Torque:

Exhaust muffler lock bolt: 3.2～3.8kgf-m
Exhaust muffler lock nut: 1.8～2.2kgf-m

Remove the nut and bolt at the exhaust
muffler, then remove the exhaust muffler.

INSTALLATION

Install by reversing the removal sequence.

Torque:

Exhaust muffler lock bolt and nut:

3.2～3.8kgf-m

N

uts

Bol

t

Gaske

t

Nut

Bol

t

Be sure to install a new exhaust gasket.

＊

3. INSPECTION/ADJUSTMENT

3-0

Mongoose/KXR 250

3

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

INSPECTION/ADJUSTMENT

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 3- 1
MAINTENANCE SCHEDULE-------------------------------------------- 3- 2
FUEL LINE/THROTTLE OPERATION/AIR CLEANER ------------ 3- 3
AIR FILTER FOR DRIVE BELT/ SPARK PLUG --------------------- 3- 6
VALVE CLEARANCE/CARBURETOR IDLE SPEED--------------- 3- 7
IGNITION TIMING/CYLINDER COMPRESSION ------------------- 3- 8
ENGINE OIL----------------------------------------------------------------- 3- 9
TRANSMISSION OIL REPLACEMENT ------------------------------- 3-10
DRIVE BELT/BRAKE PADS/BRAKE FLUID INSPECTION ------ 3-11
HEADLIGHT AIM/ STEERING SYSTEM INSPECTION ----------- 3-12
TOE-IN ADJUSTMENT --------------------------------------------------- 3-13
WHEELS/TIRES ------------------------------------------------------------ 3-14
DRIVE CHAIN SLACK ADJUSTMENT-------------------------------- 3-16
DRIVE SELECT LEVER ADJUSTMENT ------------------------------ 3-18
CABLE INSPECTION AND LUBRICATION-------------------------- 3-19
REAR SUSPENSION LUBRICATION---------------------------------- 3-19
COOLING SYSTEM-------------------------------------------------------- 3-20

3

3. INSPECTION/ADJUSTMENT

3-1

Mongoose/KXR 250

SERVICE INFORMATION

GENERAL

！ WARNING

•Before running the engine, make sure that the working area is well-ventilated. Never run the
engine in a closed area. The exhaust contains poisonous carbon monoxide gas which may
cause death to people.

•Gasoline is extremely flammable and is explosive under some conditions. The working area
must be well-ventilated and do not smoke or allow flames or sparks near the working area or
fuel storage area.

SPECIFICATIONS

ENGINE
Throttle grip free play : 1～4mm
Spark plug gap : 0.6～0.7mm
Spark plug: Standard : DPR7EA-9
Valve clearance : IN: 0.1mm

EX: 0.1mm
Idle speed : 1500±100rpm
Engine oil capacity:
At disassembly : 1.6 liter
At change : 1.4 liter
Gear oil capacity :
At disassembly : 400cc
At change : 300cc
Cylinder compression : 15±2kg/cm²
Ignition timing : BTDC 5°±1°/2000rpm

TIRE PRESSURE

1 Rider

Front 0.28kgf/cm²

Rear 0.28kgf/cm²

TIRE SIZE:
Front : 21*7-10
Rear : 20*11-9

TORQUE VALUES

Front wheel nut 4.0～5.0kgf-m
Rear wheel nut 4.0～5.0kgf-m

3. INSPECTION/ADJUSTMENT

3-2

Mongoose/KXR 250

MAINTENANCE SCHEDULE

This chapter includes all information necessary to perform recommended inspections and
adjustments. These preventive maintenance procedures, if followed, will ensure more reliable
vehicle operation and a longer service life. The need for costly overhaul work will be greatly
reduced. This information applies to vehicles already in service ad well as new vehicles that are
being prepared for sale. All service technicians should be familiar with this entire chapter.

Initial Every

Item Remarks

1

month3month6month6month

1

year

Valves

Check valve clearance. Adjust if
necessary.

○○○○

Spark plug

Check condition. Adjust gap and
clean. Replace if necessary.

○○○○○

Air filter element (for
engine and drive belt
compartment)

Clean.
Replace if necessary.

Every 20~40 hours

(

more often in wet or dusty areas.

)

Carburetor

Check idle speed/starter operation.
Adjust if necessary.

○○○○

Fuel line

Check fuel hose for cracks or
damage. Replace if necessary.

○○○

Engine oil

Replace (Warm engine before
draining).

○○○○

Coolant

Check coolant leakage.
Replace if necessary.
Replace coolant every 24 months.

○○○○○

Oil strainer

Clean.
Replace if necessary.

○○○

Drive chain

Check and adjust
slack/alignment/clean/lube.

○○○○○

Transmission oil

Check oil leakage. Replace every
12 months.

○○

Brake system

Check operation and brake fluid.
Replace brake pad if necessary.

○○○○○

Drive belt

Check operation/replace if damage
or excessive wear.

○○

Wheels

Check balance/damage/runout.
Replace if necessary.

○○○○

Wheel bearings

Check bearing assembly for
looseness/damage. Replace if
damaged.

○○○○

Steering system

Check operation/replace if damage.
Check toe-in/adjust if necessary.

○○○○○

Rear swing arm shafts Lubricate every 6 months. ○○○
Fitting/Fasteners

Check all chassis fittings and
fasteners. Correct if necessary.

○○○○○

•In the interest of safety, we recommend these items should be serviced only by an authorized

KYMCO motorcycle dealer.

3. INSPECTION/ADJUSTMENT

3-3

Mongoose/KXR 250

FUEL LINE

Check the fuel tubes and replace any parts,
which show signs of deterioration, damage
or leakage.

THROTTLE OPERATION

Check the throttle to swing for smooth
movement.
Measure the throttle to swing free play.

Free Play (A): 1～4mm
To adjust throttle free play:

Slide the rubber sleeve back to expose the
throttle cable adjuster.

Loosen the lock nut, then turn the adjuster
to obtain the correct free play. (1~4 mm or

0.04~0.16 in)
Tighten the lock nut and reinstall the sleeve.

AIR CLEANER

AIR CLEANER REPLACEMENT

Remove the seat. (See page 2-3)
Unlatch the four retainer clips and remove

the air cleaner housing cover.

Do not smoke or allow flames or sparks
in your working area.

＊

Fuel Filte

r

Fuel tubes

Lock nu

t

Retainer Clips

Air Cleaner Housing Cove

r

Cable adjuste

r

Rubber sleeve

3. INSPECTION/ADJUSTMENT

3-4

Mongoose/KXR 250

Unscrew the clamp and remove the air
cleaner assembly from the air cleaner
housing.

Remove the screw and remove the air
cleaner assembly from the air cleaner
holder.

Remove the air cleaner and air cleaner
screen from the air cleaner body.
Remove the air cleaner net from the air
cleaner.

Reassemble by reversing the disassembly
sequence.

Air Cleaner AssemblyScrew

Screw Air Cleaner Holde

r

Air Cleane

r

Air Cleaner screen

Air Cleaner body

3. INSPECTION/ADJUSTMENT

3-5

Mongoose/KXR 250

CLEAN AIR FILTER ELEMENT

Wash the element gently, but throughly in
solvent.

Squeeze the excess solvent out of the
element and let dry.

Apply the engine oil.
Squeeze out the excess oil.

More frequent replacement is required when
riding in unusually dusty or rainy areas.

AIR CLEANER HOUSING DRAIN

Remove the drain tube by removing the
clip.
Drain the deposits.
Reinstall the drain tube, securing it with the
clip.

Use parts cleaning solvent only. Neve

r

use gasoline or low flash point solvents
which may lead to a fire or explosion.

＊

Do not twist or wring out the foa

m

element. This could damage the foam
material.

＊

The element should be wet but not
dripping.

＊

Air Cleaner Housing

Drain Tube

Clip

3. INSPECTION/ADJUSTMENT

3-6

Mongoose/KXR 250

Gap, Wear, and Fouling Deposits

AIR FILTER FOR DRIVE BELT

To clean the air filter:
Remove the two screws attaching front
fender and remove air filter housing.
Remove the two screws and remove air
filter housing cover.

Remove the air filter from the housing.
Tap the air filter lightly to remove most of
the dust and dirt.
Blow out the remaining dirt with
compressed air.
If the element is damaged, replace it.

Reassemble by reversing the disassembly
sequence.

SPARK PLUG

Remove ignition coil cap and spark plug.
Check the spark plug for wear and fouling
deposits.
Clean any fouling deposits with a spark
plug cleaner or a wire brush.

Specified Spark Plug: DPR7EA-9

Measure the spark plug gap.
Spark Plug Gap: 0.6～0.7mm

Cracks, Damage

Washer Deformation

Screws

Air Filter Housing

Screw

Air Filter Cove

r

Air Filte

r

When installing, first screw in the spar

k

plug by hand and then tighten it with a
spark plug wrench.

＊

Ignition Coil Cap

Spark Plug

3. INSPECTION/ADJUSTMENT

3-7

Mongoose/KXR 250

VALVE CLEARANCE

Remove the cylinder head cover. (See page
7-4)

Turn the flywheel clockwise so that the “T”
mark on the flywheel aligns with the index
mark on the right crankcase cover to bring
the round hole on the camshaft gear facing
up to the top dead center on the
compression stroke.

Inspect and adjust the valve clearance.
Valve Clearance: IN: 0.1mm

EX: 0.1mm

Loosen the lock nut and adjust by turning
the adjusting nut

Tappet adjuster E012

CARBURETOR IDLE SPEED

Warm up the engine before this operation.
Start the engine and connect a tachometer.
Turn the throttle stop screw to obtain the
specified idle speed.

Idle Speed: 1500±100rpm

When the engine misses or run erratic,
adjust the air screw.

Inspect and adjust valve clearance while
the engine is cold (below 35℃).

＊

• The engine must be warm for accurate
idle speed inspection and adjustment.

＊

Cylinder Head Cove

r

Round Hole

Valve Wrench

Throttle Stop Screw

AirScrew

“T” Mark

• Check the valve clearance again afte

r

the lock nut is tightened.

＊

Special

Index Mark

3. INSPECTION/ADJUSTMENT

3-8

Mongoose/KXR 250

IGNITION TIMING

Remove the timing hole cap.

Check the ignition timing with a timing
light.
When the engine is running at idle speed,
the ignition timing is correct if the “F” mark
on the flywheel aligns with the index mark
on the right crankcase cover.

CYLINDER COMPRESSION

Warm up the engine before compression
test.
Remove the spark plug.
Insert a compression gauge.
Open the throttle valve fully and push the
starter button to test the compression.

Compression: 15±2kg/cm

2

If the compression is low, check for the
following:

- Leaky valves

- Valve clearance too small

- Leaking cylinder head gasket

- Worn piston rings

- Worn piston/cylinder
If the compression is high, it indicates that

carbon deposits have accumulated on the
combustion chamber and the piston head.

The ignition unit is not adjustable. If the
ignition timing is incorrect, check the
ignition system.

＊

Compression Gauge

Timing Hole

Timing Hole Cap

Index Mark

3. INSPECTION/ADJUSTMENT

3-9

Mongoose/KXR 250

ENGINE OIL

OIL LEVEL

Place the machine on a level place.
Warm up the engine for several minutes and
stop it.

Check the oil level through the inspection
window.
The oil level should be between the
maximum (H) and minimum (L) marks. If
the level is low, add oil to raise it to the
proper level.

ENGINE OIL REPLACEMENT

Place the machine on a level place.
Warm up the engine for several minutes and

stop it.
Place a container under the engine.
Remove the oil fill cap and drain plug to

drain the oil.

Reinstall the drain plug and tighten the
drain plug to specification.

Torque: 2.0～3.0kgf-m

Fill the engine with oil and install the oil fill
cap.

Oil Capacity: At disassembly: 1.6L

At change: 1.4L

Inspection Window

Lower Level

Upper Level

Run the engine for 2～3 minutes and
check the oil level after the engine is
stopped for 2～3 minutes.

＊

Oil Fill Cap

Drain Plu

g

The engine oil will drain more easily
while the engine is warm.

＊

3. INSPECTION/ADJUSTMENT

3-10

Mongoose/KXR 250

ENGINE OIL REPLACEMENT AND
OIL FILTER CLEANING

Place the machine on a level place.
Warm up the engine for several minutes and

stop it.
Place a container under the engine.
Remove the oil fill cap and oil filter cap to

drain the oil.

Clean the oil strainer with solvent.
Inspect the O-ring and replace if damaged.
Reinstall the O-ring, oil strainer,

compression spring and oil filter cap.
Tighten the oil filter cap to specification.

Torque: 1.0～2.0kgf-m

Fill the engine with oil and install the oil fill
cap.

Oil Capacity: At disassembly: 1.6L

At change: 1.4L

TRANSMISSION OIL
REPLACEMENT

Place the machine on a level place.
Place a container under the engine.
Remove the oil filler bolt and drain plug to

drain the oil.
Reinstall the drain plug and tighten to

specification.
Torque: 2.0～3.0kgf-m

Fill the engine with oil and install the oil
filler bolt.

Oil Capacity: At disassembly: 400cc

At change: 300cc

Start the engine and warm up for a few
minutes. While warming up, check for oil
leakage. If oil leakage is found, stop the
engine immediately and check for the cause.

Oil Filter Ca

p

O-ring

Com

p

ression Sprin

g

Oil Straine

r

Oil Filter Ca

p

Oil Filler Bol

t

Drain Plug

Make sure that the sealing washer is in
good condition.

＊

3. INSPECTION/ADJUSTMENT

3-11

Mongoose/KXR 250

DRIVE BELT

Remove the left crankcase cover.
Inspect the drive belt for cracks, scaling,
chipping or excessive wear.
Measure the V-belt width

Service limit: 22mm
Replace the drive belt if out of specification.

BRAKE PADS INSPECTION

A wear indicator is provided on each brake.
The indicators allows checking of brake
pads wear. Check the position of the
indicator. If the indicator reaches the wear
limit line, to replace the pads.

BRAKE FLUID INSPECTION

Check if the fluid level is below the lower
level mark through the inspection window.

Drive Bel

t

Front Calipe

r

Rear Calipe

r

Inspection Window (R/L Brake Lever)

3. INSPECTION/ADJUSTMENT

3-12

Mongoose/KXR 250

HEADLIGHT AIM

Turn the ignition switch ON and start the
engine.
Turn on the headlight switch.
Adjust the headlight aim by turning the
headlight aim adjusting screw.

STEERING SYSTEM
INSPECTION

Place the machine on a level place.
Check the steering column bushings and

bearings:
Move the handlebar up and down, and/or

back and forth.
Replace the steering column bushings and

or bearings if excessive play

Check the tie-rod ends
Turn the handlebar to the left and/or right

until it stops completely, then slightly move
the handlebar from left to right.

Replace the tie-rod ends if tie-rod end has
any vertical play.

Inspection Window (Rear Brake Pedal)

Adjust Screw

Tie-rod Ends

3. INSPECTION/ADJUSTMENT

3-13

Mongoose/KXR 250

Raise the front end of the machine so that
there is no weight on the front wheels.

Check ball joints and/or wheel bearings.
Move the wheels lately back and froth.

Replace the front arms and/or wheel
bearings if excessive free play.

TOE-IN ADJUSTMENT

Place the machine on a level place.
Measure the toe-in
Adjust if out of specification.
Toe-in measurement steps:
Mark both front tire tread centers.
Raise the front end of the machine so that

there is no weight on the front tires.
Fix the handlebar straight ahead.
Measure the width A between the marks.
Rotate the front tires 180 degrees until the

marks come exactly opposite.
Measure the width B between the marks.
Calculate the toe-in using the formula given

below.
Toe-in = B－A
Toe-in: 0～10mm
If the toe-in is incorrect, adjust the toe-in

Adjust the toe-in step:

Mark both tie-rods ends.
This reference point will be needed during
adjustment.
Loosen the lock nuts (tie-rod end) of both
tie-rods
The same number of turns should be given
to both tie-rods right and left until the
specified toe-in is obtained, so that the
lengths of the rods will be kept the same.

Tighten the rod end locknuts of both tie­rods

Torque: 2.5～3.5kgf-m

A

B

Tie-rod

Tie-rod End Nuts

3. INSPECTION/ADJUSTMENT

3-14

Mongoose/KXR 250

WHEELS/TIRES

Check the tires for cuts, imbedded nails or
other damages.
Check the tire pressure.

TIRE PRESSURE

1 Rider

Front 0.28kgf/cm²
Rear 0.28kgf/cm²

TIRE SIZE

Front: 21*7-10
Rear : 20*11-9

Check the front axle nut for looseness.
Check the rear axle nut for looseness.
If the axle nuts are loose, tighten them to the
specified torque.

Torque: Front : 6.0～8.0kgf-m
Rear : 9.0～11.0kgf-m

Front Axle Nu

t

RearAxle Nu

t

• Be sure that both tie-rod are turned the
same amount. If not, the machine will
drift tight or left even though the
handlebar is positioned straight which
may lead to mishandling and accident.

• After setting the toe-in to specification,
run the machine slowly for some
distance with hands placed lightly on
the handlebar and check that the
handlebar responds correctly. If not,
turn either the right or left tie-rod
within the toe-in specification.

＊

Tire pressure should be checked when
tires are cold.

＊

Tie-rod

Tie-rod End Nuts

3. INSPECTION/ADJUSTMENT

3-15

Mongoose/KXR 250

Inspect the tire surfaces.
Replace if wear or damage.

Tire wear limit: 3.0mm

WHEEL INSPECTION

Inspect the wheel.
Replace if damage or bends
Always balance the wheel when a tire or

wheel has been changed or replaced.

• Never attempt even small repairs to the
wheel.

• Ride conservatively after installing a
tire to allow it to seat itself properly on
the rim.

＊

It is dangerous to ride with a worn out
tire. When a tire wear is out of
specification, replace the tire
immediately.

＊

3. INSPECTION/ADJUSTMENT

3-16

Mongoose/KXR 250

DRIVE CHAIN SLACK
ADJUSTMENT

Before checking and/or adjusting, rotate the
rear wheels several revolutions and check
slack at several points to find the tightest
point. Check and/or adjust the chain slack
with the rear wheels in this “tightest”
position.

Place the machine on a level place.

Check drive chain slack.
Adjust if out of specification.

Drive chain slack (A): 30 ~ 40mm

Adjust drive chain slack:
Loosen the caliper holder bolt and two axle

hub holding bolt.

Provide a proper pin and pass the pin
through the axle hub and driven sprocket.

Bol

t

Too little of chain slack will overload the
engine and other vital parts; keep the

＊

Wheels should be on the ground without

＊

Bolts

Driven Sprocke

t

Pin

Axle Hub

3. INSPECTION/ADJUSTMENT

3-17

Mongoose/KXR 250

To tighten the chain, push the ATV
forward.

To loosen the chain, pull the ATV
backward.

Retighten the two axle hub holder bolt and
caliper holder bolt to the specification.

Torque:
Axle hub holding bolt: 3.5～4.5kgf-m
caliper holder bolt: 0.8～1.2kgf-m

Pull out the pin.

Bol

t

Bolts

Pin

3. INSPECTION/ADJUSTMENT

3-18

Mongoose/KXR 250

DRIVE SELECT LEVER
ADJUSTMENT

Turn the ignition switch is ON and make
sure the engine stop switch in the OFF
position.

Loosen the lock nuts of rod.
Shift the gear to neutral by moving the shift

lever and/or turn the rod. (The neutral
indicator lamp comes on.)

Provide standard/phillips screwdriver and
pass the standard/phillips screwdriver
through the shift arm into the index hole at
the transmission case cover.

Turn the rod clockwise or counterclockwise
until the drive select lever into the "N"
position of the shift guide and tighten the
lock nuts, then pull out the standard/phillips
screwdriver.

After adjustment, start the engine and test to
ride the ATV to be sure the drive select
lever is operating properly.

Lock Nuts

Rod

Standard/Phillips Screwdrive

r

Shift Ar

m

Index Hole

Drive Leve

r

Rod

3. INSPECTION/ADJUSTMENT

3-19

Mongoose/KXR 250

CABLE INSPECTION AND
LUBRICATION

Inspect the cable sheath.
Replace if damage.
Check the cable operation.
Lubricate or replace if unsmooth operation.

LEVER LUBRICATION

Lubricate the pivoting parts of each lever.

REAR SUSPENSION
LUBRICATION

Inject grease into the nipples using a grease
gun until slight over flow is observed from
the thrust covers.

N

ipple

Damaged cable sheath may cause
corrosion and interfere with the cable
movement. An unsafe condition may
result so replace such cable as soon as
possible.

＊

Wipe off the excess grease.

＊

Hold cable end high and apply several
drops of lubricant to cable.

＊

3. INSPECTION/ADJUSTMENT

3-20

Mongoose/KXR 250

COOLING SYSTEM

COOLANT LEVEL INSPECTION

Place the machine on the level ground.
Check the coolant level in the coolant

reservoir when the engine is cold as the
coolant level will vary with engine
temperature. The coolant level should be
between the maximum and minimum marks.

If the level is low, remove the coolant
reservoir cap, and then add coolant or
distilled water to raise it to the specified
level.

Recommended Coolant: SIGMA Coolant
(Standard Concentration 30%)

COOLANT REPLACEMENT

Remove the front fender. (Ö2-5)
Remove the radiator cap.
Remove the drain bolt to drain the coolant.
Drain the coolant in the reserve tank.
Reinstall the drain bolt.

Coolant capacity: 1400cc
Radiator capacity: 1100cc
Reserve tank capacity: 300cc
Start the engine and check if there are no

bubbles in the coolant and the coolant level
is stable. Reinstall the radiator cap.

If there are bubbles in the coolant, bleed air
from the system.

Fill the reserve tank with the recommended
coolant up to the maximum mark.

The coolant level does not change no
matter the engine is warm or cold. Fill to
the maximum mark.

＊

Perform this operation when the engine
is cold.

＊

The coolant freezing point should be 5
°C lower than the temprature of the
riding area.

＊

Minimum Mark

Maximum Mark

Coolant Reservoir Cap

Drain Bol

t

4. LUBRICATION SYSTEM

4-0

Mongoose/KXR 250

4

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

LUBRICATION SYSTEM

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 4- 2
TROUBLESHOOTING----------------------------------------------------- 4- 2
ENGINE OIL/OIL FILTER ------------------------------------------------ 4- 3
OIL PUMP-------------------------------------------------------------------- 4- 3

4

4. LUBRICATION SYSTEM

4-1

Mongoose/KXR 250

LUBRICATION SYSTEM

Oil Pump

Oil Filter Screen

Crankshaft

Rocker Arm Shaft

4. LUBRICATION SYSTEM

4-2

Mongoose/KXR 250

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• The maintenance of lubrication system can be performed with the engine installed in the frame.

• Use care when removing and installing the oil pump not to allow dust and foreign matters to

enter the engine and oil line.

• Do not attempt to disassemble the oil pump. The oil pump must be replaced as a set when it
reaches its service limit.

• After the oil pump is installed, check each part for oil leaks.

SPECIFICATIONS

Item Standard (mm) Service Limit (mm)

Inner rotor-to-outer rotor clearance 0.15 0.20

Oil pump Outer rotor-to-pump body clearance 0.15～0.20 0.25

Rotor end-to-pump body clearance 0.04～0.09 0.12

TROUBLESHOOTING

Oil level too low Poor lubrication pressure

• Natural oil consumption • Oil level too low

• Oil leaks • Clogged oil filter or oil passages

• Worn or poorly installed piston rings • Not use the specified oil

• Worn valve guide or seal

4. LUBRICATION SYSTEM

4-3

Mongoose/KXR 250

Bolts

ENGINE OIL/OIL FILTER

OIL LEVEL AND OIL CHANGE

Refer to the “ENGINE OIL” section in the
chapter 3 to check the oil level and
replacement and oil filter cleaning.

OIL PUMP

REMOVAL

Remove the right crankcase cover and the
A.C. generator flywheel. (Refer to the “A.C.
GENERATOR/FLYWHEEL” section in the
chapter 16)

Remove the starter clutch gear. (Refer to the
“STARTER CLUTCH” section in the
chapter 18)

Remove the two bolts and oil separator
cover.

Pry the circlip off and remove the oil pump
driven gear, then remove the oil pump drive
chain and oil driven sprocket.

Oil Separator Cove

r

Circlip

4. LUBRICATION SYSTEM

4-4

Mongoose/KXR 250

Screw

Pump Body

Remove the two oil pump bolts for remove
the oil pump.

OIL PUMP DISASSEMBLY

Remove the screw and disassemble the oil
pump.

INSPECTION

Measure the rotor end-to-pump body
clearance.
Service Limit: 0.12mm

Oil Pump Driven Sprocke

t

Oil Pump Drive Chain

Oil Pump Bolts

4. LUBRICATION SYSTEM

4-5

Mongoose/KXR 250

Outer Roto

r

Outer Roto

r

Inner Roto

r

Pump Body

Inner Roto

r

Dowel Pin

Pum

p

Cove

r

Measure the inner rotor-to-outer rotor
clearance.
Service Limit: 0.2mm

Measure the pump body-to-outer rotor
clearance.

Service Limit: 0.25mm

ASSEMBLY

Install the outer rotor, inner rotor and pump
shaft into the pump body.

Install the dowel pin.
Install the pump cover by aligning the hole
in the cover with the dowel pin.

Tighten the screw to secure the pump cover.

INSTALLATION

Reverse the “OIL PUMP REMOVAL”
procedures.

Outer Roto

r

Oil Pump Bolts

Insert the pump shaft by aligning the flat
on the shaft with the flat in the inner
rotor.

＊

Install the oil pump with the arrow on
the pump body facing up and fill the oil
pump with engine oil before installation.

＊

4. LUBRICATION SYSTEM

4-6

Mongoose/KXR 250

Pump Shaf

t

Make sure that the pump shaft rotates freely
without binding.

Install oil pump driven sprocket and drive
chain, circlip and oil separator cover.

5. FUEL SYSTEM

5-0

Mongoose/KXR 250

5

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

FUEL SYSTEM

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 5- 2
TROUBLESHOOTING----------------------------------------------------- 5- 3
FUEL TANK ----------------------------------------------------------------- 5- 4
FUEL VALVE REMOVAL------------------------------------------------ 5- 4
THROTTLE VALVE---------------------------------------------------------- 5- 7
CARBURETOR-------------------------------------------------------------- 5- 8
AIR CLEANER -------------------------------------------------------------- 5-12

5

5. FUEL SYSTEM

5-1

Mongoose/KXR 250

5. FUEL SYSTEM

5-2

Mongoose/KXR 250

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• Do not bend or twist control cables. Damaged control cables will not operate smoothly.

• When disassembling fuel system parts, note the locations of O-rings. Replace them with new

ones during reassembly.

• Before float chamber disassembly, loosen the drain screw to drain the residual gasoline into a
clean container.

• After the carburetor is removed, plug the intake manifold side with a clean shop towel to prevent
foreign matters from entering.

• When cleaning the carburetor air and fuel jets, the O-rings and diaphragm must be removed first
to avoid damage. Then, clean with compressed air.

• When the motorcycle is not used for over one month, drain the residual gasoline from the float
chamber to avoid erratic idling and clogged slow jet due to deteriorated fuel.

SPECIFICATIONS

Item Standard
Type PD
Venturi dia. φ22
Float level 14.8mm
Main jet No. 98
Adjust method Piston
Idle speed 1500±100rpm
Throttle grip free play 1～4mm
Air screw opening 11/8±1/2

Gasoline is very dangerous. When working with gasoline, keep sparks and flames away
from the working area.
Gasoline is extremely flammable and is explosive under certain conditions. Be sure to
work in a well-ventilated area.

5. FUEL SYSTEM

5-3

Mongoose/KXR 250

SPECIAL TOOL

Float level gauge

TROUBLESHOOTING

Engine cranks but won’t start Engine lacks power

• No fuel in tank • Clogged air cleaner

• No fuel to carburetor • Faulty carburetor

• Cylinder flooded with fuel • Faulty ignition system

• No spark at plug

• Clogged air cleaner Lean mixture

• Intake air leak • Clogged carburetor fuel jets

• Improper throttle operation • Float level too low

• Intake air leak

Engine idles roughly, stalls or runs poorly • Clogged fuel tank cap breather hole

• Excessively used choke • Kinked or restricted fuel line

• Ignition malfunction

• Faulty carburetor Rich mixture

• Poor quality fuel • Float level too high

• Lean or rich mixture • Clogged air jets

• Incorrect idle speed • Clogged air cleaner

Misfiring during acceleration

• Faulty ignition system

• Faulty carburetor

Backfiring at deceleration

• Float level too low

• Incorrectly adjusted carburetor

• Faulty exhaust muffler

5. FUEL SYSTEM

5-4

Mongoose/KXR 250

FUEL TANK

REMOVAL

Remove the seat, right and left side frame
cover (See page 2-3) and center frame cover
(See page 2-5).

Switch the fuel valve “OFF”.
Disconnect the fuel tube from carburetor and
remove two screws at the fuel valve holder.

Remove the two bolts and two nuts at the
fuel tank, then remove the fuel tank.

INSTALLATION

Reverse the “FUEL TANK REMOVAL”
procedures.

FUEL VALVE

REMOVAL

Remove the screw and then remove control
switch.
Disconnect all fuel tubes and remove the two
screws, then remove fuel valve.

Warnin

g

N

uts

Fuel Tank

Screw

Fuel Valve

Screws

Fuel Tube

• Keep sparks and flames away from the
work area.

• Wipe off any spilled gasoline.

Control Switch

Screws

Fuel Valve

• Keep sparks and flames away from the
work area.

• Drain gasoline into a clean container.

＊

Fuel Tube Fuel Tubes

5. FUEL SYSTEM

5-5

Mongoose/KXR 250

DISASSEMBLY

Remove the two screws on the retaining ring
and then remove retaining ring.
Remove the washer and control shaft.

Remove the rubber gasket from the fuel
valve body.

INSPECTION

Inspect the fuel valve body for dirt and clog.
Clean if necessary.

Replace the rubber gasket with new ones if
they are damaged or deteriorated.

Replace the O-rings with new ones if they
are damaged or deteriorated.

ASSEMBLY

Reverse the “DISASSEMBLY” procedures.
Install rubber gasket, control shaft, washer

and retaining ring.

Fuel Valve Body

Control Shaf

t

Rubber Gaske

t

Retaining Ring

Washe

r

Screws

Control Shaf

t

O-ring

• Aligning the tab on the control shaft
with the outlet duct in the fuel valve
body.

• Aligning the tab on the retaining ring
with the outlet duct in the fuel valve
body.

＊

Tab

Outlet Duc

t

Outlet Duc

t

Tab

5. FUEL SYSTEM

5-6

Mongoose/KXR 250

INSTALLATION

Reverse the “FUEL VALVE REMOVEAL”
procedures.

Connect all fuel tube.

Reserve Fuel Tube

Main Fuel Tube

Outlet Fuel Tube

5. FUEL SYSTEM

5-7

Mongoose/KXR 250

THROTTLE VALVE

DISASSEMBLY

Remove the fuel tank. (Refer to “FUEL
TANK” section in the chapter 5)

Remove the carburetor cap.

Pull out the throttle valve.

Compress the spring to disconnect the
throttle cable by hand.

Remove the spring from the throttle valve

Carburetor Cap

Spring

Throttle Valve

Throttle Cable

5. FUEL SYSTEM

5-8

Mongoose/KXR 250

Pry off the needle retainer and remove the jet
needle.
Check the throttle valve and jet needle for
wear or damage.

ASSEMBLY

Reverse the “DISASSEMBLY” procedures.

Install the throttle valve into the carburetor
body.

CARBURETOR

REMOVAL

Remove the fuel tank and carburetor cap.
(Refer to “FUEL TANK” and “THROTTLE
VALVE DISASSEMBLY” section in the
chapter 5)
Loosen the drain screw to drain the gasoline
from the float chamber.

Loosen the screw on the lock plate for
disconnect the choke cable.

Throttle Valve

N

eedle Retaine

r

Jet Needle Clip

Fuel Drain Plu

g

Choke Cable

Screw

Align the groove in the throttle valve
with the throttle stop screw on the
carburetor body.

＊

Throttle Stop Screw

Groove

• Keep sparks and flames away from the
work area.

• Drain gasoline into a clean container.

＊

5. FUEL SYSTEM

5-9

Mongoose/KXR 250

Remove the two bolts at the air cleaner case.
Loosen the air cleaner connecting tube band

screw.
Remove the two carburetor lock nuts
attaching the inlet pipe.
Remove the carburetor

DISASSEMBLY

Remove the float chamber attaching three
screws and remove the float chamber.

Remove the jet holder.

Pull out the float pin, then remove float and
float valve.

Jet Holde

r

Bolts

Band

Screws

Float Valve

Float Pin

Floa

t

N

uts

Float Chambe

r

5. FUEL SYSTEM

5-10

Mongoose/KXR 250

Remove the main jet, needle jet holder, and
needle jet.
Remove the slow jet.
Remove the air screw and throttle stop
screw.

CAUTIONS!

Remove the two screws and the air cut-off
valve cover.

Screws

Air Screw

Slow Je

t

Main Je

t

Throttle Stop Screw

Sprin

g

Washe

r

O-ring

Air Screw

Throttle St o p S c r e

w

Sprin

g

Slow Je

t

Main Je

t

N

eedle Jet Holde

r

N

eedle Je

t

• Be careful not to damage the jets an

d

jet holder when removing them.

• Before removal, turn the throttle stop
screw and air screw in and count the
number of turns until they seat lightly
and then make a note of this.

• Do not force the screw against its seat
to avoid seat damage.

• Be sure to install the O-ring in the
reverse order of removal.

＊

5. FUEL SYSTEM

5-11

Mongoose/KXR 250

Remove the spring, diaphragm and O-rings.
Inspect the diaphragm and spring for wear or
damage.

CARBURETOR CLEANING

Blow compressed air through all passages of
the carburetor body.

FLOAT/FLOAT VALVE INSPECTION

Inspect the float valve seat for wear or
damage.
Inspect the float for damage or fuel level
inside the float chamber.

FUEL RESERVOIR O-RING CHECK

Remove the O-ring.
INSPECTION

Inspect the check the O-ring for damage.
Replace with new ones if necessary

Spring

Dia

p

hra

gm

Cove

r

O-ring

Float Valve

Float Valve Sea

t

O-rin

g

5. FUEL SYSTEM

5-12

Mongoose/KXR 250

ASSEMBLY

Install the slow jet.
Install the needle jet, needle jet holder and
main jet.
Install the throttle stop screw and air screw
Install the spring, diaphragm and O-rings.

Install the float valve, float and float pin.

FLOAT LEVEL INSPECTION

Turn the carburetor upside down so that the
float will go down to make the float valve
contact the float valve seat.
Then slowly tilt the carburetor and measure
the float level with the float level gauge
while the float pin just contacts with float
valve.

Float Level: 14.8mm

When adjusting, carefully bend the float pin.
Check the float for proper operation.

Install the jet holder, aligning the jet holder
groove with the carburetor tab and then
install the float chamber.

INSTALLATION

Reverse the “ CARBURETOR REMOVAL”
procedures.

AIR CLEANER

Refer to the “AIR CLEANER” section in the
chapter 3 for air cleaner replacement and
cleaning.

• When installing the air screw, return it
to the original position as noted during
removal

• After the carburetor is installed, be
sure to perform the Exhaust Emission

＊

Jet Holde

r

6. ENGINE REMOVAL

6-0

Mongoose/KXR 250

6

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

ENGINE REMOVAL

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 6- 1
ENGINE REMOVAL ------------------------------------------------------- 6- 2

6

6. ENGINE REMOVAL/INSTALLATION

6-1

Mongoose/KXR 250

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• A floor jack or other adjustable support is required to support and maneuver the engine.
Be careful not to damage the machine body, cables and wires during engine removal.

• Use shop towels to protect the machine body during engine removal.

• Parts requiring engine removal for servicing:

⎯ Crankcase
⎯ Crankshaft

6. ENGINE REMOVAL

6-2

Mongoose/KXR 250

ENGINE REMOVAL

Drain engine oil and transmission oil.
(Refer to chapter 3)
Remove frame covers and exhaust pipe.
(Refer chapter 2)
Remove the carburetor. (Refer to chapter 5)

Disconnect the oil recycle tube at the
cylinder head cover.

Disconnect the water hose from water pump
cover.

Remove the bolt at the thermostat and
disconnect the thermosensor wire, then
disconnect the thermostat from the cylinder
head.

Remove the bolt at the drive select arm,
then disconnect the drive select arm from
engine assembly.

Oil Recycle Tube

Water Hose

Bol

t

Thermosensor Wire

Thermosta

t

Drive Select Ar

m

Bol

t

6. ENGINE REMOVAL/INSTALLATION

6-3

Mongoose/KXR 250

Disconnect the speedometer cable (ON
ROAD only).

Remove the three bolts at the drive sprocket
cover and then remove the drive sprocket
cover.

Remove the two bolts on the drive sprocket.
Remove the drive sprocket and washer.

Slide the rubber sleeve back to expose the
starter motor wire nut.

Remove the starter motor wire nut for
disconnect the starter motor wire.

Remove the bolt at the starter motor for
disconnect the ground wire lead.

Bolts

Drive Sprocket Cove

r

Bolts

Drive Sprocke

t

Rubber Sleeve

Nut

Bol

t

Ground Wire

Speedometer Cable

6. ENGINE REMOVAL

6-4

Mongoose/KXR 250

Remove the A.C.Generator, pulser and gear
change switch couplers.

Disconnect the spark plug cap.

Remove the three bolts and remove the
outlet hose cover.

Unscrew the clamp and then disconnect the
outlet hose from the left crankcase cover.

Unscrew the clamp and then disconnect the
inlet hose from the left crankcase cover.

Gear Change Switch couple

r

A.C.Generator couple

r

Pulser couple

r

Spark Plug Cap

Bolts

Outlet Hose Cove

r

Screw Screw

Outlet Hose

Inlet Hose

6. ENGINE REMOVAL/INSTALLATION

6-5

Mongoose/KXR 250

Remove the two bolts at the left foot peg
attaching the left floor board holder and
remove the nut at the left floor board holder,
then remove the left floor board holder.

Remove the two bolts at the right foot peg
attaching the right floor board holder.

Remove the nut at the right floor board
holder and bolt attaching the reservoir
protection cover, then remove the right floor
board holder.

Remove the two nuts and then remove the
drive select lever.

Remove the two bolts at the left front fender
holder for remove the left front fender
holder.

Bolts

Nut

Nut

Bolts

Bol

t

Reservoir protection Cove

r

N

uts

Drive Select Leve

r

Left Front Fender Holde

r

Bolts

6. ENGINE REMOVAL

6-6

Mongoose/KXR 250

Remove the rear lower mounting bolt and
nut.

Remove the rear upper mounting bolt and
nut.

Remove the front mounting bolts and nuts.

Remove the four bolts for remove the left
and right engine brackets.

Remove the engine assembly to the left side
of the machine.

Mounting Bolt and Nu

t

Mounting Bolt and Nu

t

Mounting Bolt and Nu

t

Bolts

Brackets

6. ENGINE REMOVAL/INSTALLATION

6-7

Mongoose/KXR 250

7. CYLINDER HEAD/VALVES

7-0

Mongoose/KXR 250

7

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

__________________________________________________________________________________

CYLINDER HEAD/VALVES

__________________________________________________________________________________

SERVICE INFORMATION------------------------------------------------ 7- 2
TROUBLESHOOTING----------------------------------------------------- 7- 3
CYLINDER HEAD COVER----------------------------------------------- 7- 4
CAMSHAFT/CAMSHAFT HOLDER------------------------------------ 7- 4
CYLINDER HEAD---------------------------------------------------------- 7- 9

7

7. CYLINDER HEAD/VALVES

7-1

Mongoose/KXR 250

7. CYLINDER HEAD/VALVES

7-2

Mongoose/KXR 250

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• The cylinder head can be serviced with the engine installed in the frame.

• When assembling, apply molybdenum disulfide grease or engine oil to the valve guide movable

parts, valve arm and camshaft sliding surfaces for initial lubrication.

• The camshaft is lubricated by engine oil through the cylinder head engine oil passages. Clean and

unclog the oil passages before assembling the cylinder head.

• After disassembly, clean the removed parts and dry them with compressed air before inspection.

• After removal, mark and arrange the removed parts in order. When assembling, install them in

the reverse order of removal.

SPECIFICATIONS

Item Standard (mm) Service Limit (mm)

IN 0.1 ⎯

EX 0.1 ⎯

Cylinder head compression pressure 15±2kg/cm²
Cylinder head warpage ⎯ 0.05

IN 34.287 34.15

EX 34.1721 34.05

Valve rocker arm to shaft clearance

0.034～0.09 0.1
Valve stem-to-guide IN 0.010～0.037 0.06
clearance

EX 0.025～0.052 0.08

IN 30.9 29.4

Valve spring free length

EX 41 39

IN 10.20～11.84kg(at 18.05mm) ⎯

Valve spring
compressed force

EX 19.14～22.02kg(at 21.5mm) ⎯

IN 0.8 ⎯

Valve spring tilt

EX 1.07 ⎯

Valve clearance (cold)

Camshaft cam height

7. CYLINDER HEAD/VALVES

7-3

Mongoose/KXR 250

TORQUE VALUES

Cylinder head cover bolt 0.8～1.2kgf-m
Cam shaft hold nut 2.3～2.7kgf-m Apply engine oil to threads
Tappet adjusting nut 0.7～1.1kgf-m

SPECIAL TOOLS

Valve spring compressor E040
Tappet adjuster E012

TROUBLESHOOTING

• The poor cylinder head operation can be diagnosed by a compression test or by tracing engine
top-end noises.

Poor performance at idle speed White smoke from exhaust muffler

• Compression too low • Worn valve stem or valve guide

• Damaged valve stem seal

Compression too low

• Incorrect valve clearance adjustment Abnormal noise

• Burned or bend valves • Incorrect valve clearance adjustment

• Incorrect valve timing • Sticking valve or broken valve spring

• Broken valve spring • Damaged or worn camshaft

• Poor valve and seat contact • Worn cam chain guide

• Leaking cylinder head gasket • Worn camshaft and rocker arm

• Warped or cracked cylinder head

• Poorly installed spark plug

Compression too high

• Excessive carbon build-up in combustion
chamber

7. CYLINDER HEAD/VALVES

7-4

Mongoose/KXR 250

CYLINDER HEAD COVER

REMOVAL

Remove fuel tank. (Refer to the chapter 5)

Disconnect the oil recycle tube at the
cylinder head cover.

Remove the four bolts at the cylinder head
cover, then remove the cylinder head cover.

INSTALLATION

Install a new cylinder head cover O-ring
and install the cylinder head cover.
Install and tighten the cylinder head cover
bolts.

Torque: 0.8～1.2kgf-m

CAMSHAFT/CAMSHAFT
HOLDER

REMOVAL

Remove the cylinder head cover. (Refer to
the cylinder head cover removal)

Remove the cam chain tensioner cap bolt
and the O-ring.

Turn the cam chain tensioner screw
clockwise to tighten it.

Cylinder Head Cove

r

Oil Recycle Tube

Bolts

O-ring

Be sure to install the O-ring into the
groove properly.

＊

Bol

t

Tensioner Screw

7. CYLINDER HEAD/VALVES

7-5

Mongoose/KXR 250

Remove the four camshaft holder nuts and
washers.

Remove the camshaft holder and dowel
pins.

Remove the camshaft gear from the cam
chain and remove the camshaft.

CAMSHAFT HOLDER DISASSEMBLY

Take out the valve rocker arm shafts.
Remove the valve rocker arms, arm shafts
and stop plate.

Diagonally loosen the cylinder head nuts
in 2 or 3 times.

＊

Nut

s and Washers

Camshaft Holde

r

Camshaf

t

Stop Plate

Rocker Ar

m

s

Rocker Arm Shaf

t

s

7. CYLINDER HEAD/VALVES

7-6

Mongoose/KXR 250

CAMSHAFT HOLDER INSPECTION

Inspect the camshaft holder for wear or
damage.

Inspect the rocker arm shaft for blue
discoloration or grooves.

If any defects are found, replace the rocker
arm shaft with a new one, then inspect
lubrication system.

Inspect the rocker arm bore, cam lobe
contact surface and adjuster surface for
wear/pitting/scratches/blue discoloration.

If any defects are found, replace the rocker
arm shaft with a new one, then inspect
lubrication system.

Measure each rocker arm shaft O.D.
Measure the I.D. of each valve rocker arm.
Measure arm to shaft clearance.
Replace as a set if out of specification.

Service limits: 0.10mm

Camshaft Holde

r

Rocker Arm Shafts

Rocker Arm Bore

Contact Surface Adjuster Surface

7. CYLINDER HEAD/VALVES

7-7

Mongoose/KXR 250

CAMSHAFT HOLDER ASSEMBLY

Reverse the “CAMSHAFT HOLDER
DISASSEMBLY” procedures.

CAMSHAFT INSPECTION

Check each camshaft bearing for play or
damage. Replace the camshaft assembly
with a new one if the bearings are noisy or
have excessive play.

Inspect camshaft lobes for
pitting/scratches/blue discoloration.

Measure the cam lobe height.

Service Limits:

IN : 34.15mm replace if below
EX: 34.05mm replace if below
If any defects are found, replace the

camshaft with a new one, then inspect
lubrication system.

Camshaft Bearings

Align the cross cutout on the exhaust
valve rocker arm shaft with the bolt of

＊

7. CYLINDER HEAD/VALVES

7-8

Mongoose/KXR 250

INSTALLATION

Reverse the “CAMSHAFT REMOVAL”
procedures.

Note the following points:

1. Turn the flywheel so that the “T” mark on

the flywheel aligns with the index mark
on the crankcase.
Keep the round hole on the camshaft
gear facing up and align the punch marks
on the camshaft gear with the cylinder
head surface (Position the intake and
exhaust cam lobes down.) and install the
camshaft onto the cylinder head. (Refer
to the “VALVE CLEARANCE” section
in the chapter 3)

Install the camshaft dowel pins and
holder.

Torque:

Cam shaft hold nut: 2.3～2.7kgf-m Apply engine oil to threads

2. Turn the cam chain tensioner screw

counter-clockwise to release it.
Apply engine oil to a new O-ring and

install it.
Tighten the cam chain tensioner cap bolt.

3. Adjust the valve clearance. (Refer to the

“VALVE CLEARANCE” section in the
chapter 3)

• Apply engine oil to the threads of the
cylinder head nuts.

• Diagonally tighten the cylinder head
nuts in 2～3 times.

＊

Be sure to install the O-ring into the
groove properly.

＊

Dowel Pins

7. CYLINDER HEAD/VALVES

7-9

Mongoose/KXR 250

CYLINDER HEAD

REMOVE

Remove the camshaft. (Refer to the
“camshaft remove” section in the chapter 7)
Remove the carburetor. (Refer to the
“carburetor remove” section in the chapter

5)
Remove the exhaust muffler. (Refer to the
“exhaust muffler remove” section in the
chapter 2)

Remove the two bolts and then remove the
carburetor intake manifold.

Remove the bolt and disconnect the
thermostat.

Remove the two cylinder head bolts.
Remove the cylinder head.

CYLINDER HEAD DISASSEMBLY

Remove the valve spring cotters, retainers,
springs, spring seats, oil seals and valves
using a valve spring compressor.

Valve Spring Compressor E040

Bolts

Intake Manifold

Bol

t

Bol

t

Bolts

Valve Cotte

r

RetainerSprings Springs Sea

t

Oil Seal

Valve

Spring Compresso

r

• Be sure to compress the valve springs
with a valve spring compressor.

• Mark all disassembled parts to ensure
correct reassembly.

＊

Special

7. CYLINDER HEAD/VALVES

7-10

Mongoose/KXR 250

VALVE /VALVE GUIDE INSPECTION

Inspect each valve for bending, burning,
scratches or abnormal stem wear.
If any defects are found, replace the valve
with a new one.

Check valve movement in the guide.
Measure each valve stem O.D.

Measure each valve guide I.D.
Subtract each valve stem O.D. from the

corresponding guide I.D. to obtain the stem­to-guide clearance.

Service limits: IN : 0.06mm replace if over

EX: 0.08mm replace if over

CYLINDER HEAD INPECTION

Check the spark plug hole and valve areas
for cracks.
Check the cylinder head for warpage with a
straight edge and feeler gauge.
Service Limit: 0.05mm repair or replace if
over

VALVE SPRING INSPECTION

Measure the free length of the inner and
outer valve springs.

Service Limit:

Inner: 29.4mm replace if below
Outer: 39mm replace if below

If the stem-to-guide clearance exceeds
the service limits, replace the cylinder
head as necessary.

＊

7. CYLINDER HEAD/VALVES

7-11

Mongoose/KXR 250

Measure compressed force (valve spring)
and installed length.
Replace if out of specification.

Service limits:
IN : 10.20～11.84kg(at 18.05mm)

EX : 19.14～22.02kg(at 21.5mm)

Measure the spring tilt.
Replace if out of specification.

Service limits: IN : 0.8mm
EX : 1.07mm

7. CYLINDER HEAD/VALVES

7-12

Mongoose/KXR 250

ASSEMBLY

Install the valve spring seats and oil seal.

Lubricate each valve with engine oil and
insert the valves into the valve guides.

Install the valve springs and retainers.

Compress the valve springs using the valve
spring compressor, then install the valve
cotters.

Valve Spring Compressor E040

Tap the valve stems gently with a plastic
hammer for 2～3 times to firmly seat the
cotters.

INSTALLATION

Install the dowel pins and a new cylinder
head gasket.

Reverse the “CYLINDER HEAD
REMOVAL” procedures.

Torque:

Cylinder head bolt: 0.8～1.2kgf-m

Dowel Pins

Gaske

t

• When assembling, a valve spring
compressor must be used.

• Install the cotters with the pointed ends
facing down from the upper side of the
cylinder head.

＊

Special

Be sure to install new oil seal.

＊

Be careful not to damage the valves.

＊

8. CYLINDER/PISTON

8-0

Mongoose/KXR 250

8

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CYLINDER /PISTON

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SERVICE INFORMATION------------------------------------------------ 8- 2
TROUBLESHOOTING----------------------------------------------------- 8- 2
CYLINDER/PISTON ------------------------------------------------------- 8- 4

8

8. CYLINDER/PISTON

8-1

Mongoose/KXR 250