Harley Davidson MX 250 1978 Owner's manual

1978

Owner's

Manual

MX

25O

COMPETITION

MODEL

IMPORTANT

NOTICE

The MX-250

Inc. without

factured

federal

public

Some

streets,

state laws

Model warranty.

for

competition

motor

roads

vehicle

prohibit

an organized racing

course which

ed

sanctioning

governmental

For

off-road

additional

Such

spark

with

noise

Performance

n

ecessa ry

This motorcycle

model.

only

permit

cycle, first

For

owner's

carrying

_safe

is conducted urider

body or

authority having

use

other than

spark

arrester-muffler may

arresters

level

and spark

wilt

.

is

The vehicle

passenger.

a

determine

operation

manual

HARLEY-DAVIDSON

carefully.

is sold by Harley-Davidson

This vehicle

use

only. lt

safety

highways

or

operation

or competitive

by

is designed

does not

standards

is illegal.

of this vehicle

event

the

auspices of

permit

issued

and operation

jurisdiction.

sanctioned

are available

arrester

be decreased

designed

that operation

and

and constructed

load limit

Before

proper

MOTOR

commercially

and

maintenance,

racing

required

be

laws

and regulations.

retuning

and seat operating

legal.

is

CO., INC.

Motor

and manu-

conform

except

upon

recogniz-

a

by

the local

events,

to comply

as

an operator

do not

your

read

Co.,

on

a closed

an

by law.

may

be

safely

motor-

the

to

in

YOUR

OWNER'S

MANUAL

Welcome

designed pared

to the Harley-Davidson

and manufactured provide

to

the instructions

Your

owner's

Harley-Davidson

properly

maintain

to be

a simple

carefully

manual

dealer

this vehicle.

TECHNICAL

OPE RATI

I

NSPECTION

MAINTENANCE TROUBLESHOOTING MAINTENANCE SERVICE

and understandable guide

for its

contains

has

instructions

facilities,

the

DATA

NG INSTRUCTIONS

AND

SPECI FICATIONS

Motorcycling

finest

the

maximum

in

performance

experience

TABLE

Section

ADJUSTMENTS

SCHEDULE

Familyl

its field.

for

owner

OF CONTENTS

for

and

Your

The

your

and

care,

genuine

new

Harley-Davidson

instructions

motorcycle's

your

personal

maintenance

Harley-Davidson

in

this book

operation

motorcycling

and minor

Page

2

7

I

16

24 25 26

Motorcycle

have

and care.

repair.

parts

necessary

Motor

pre-

been

Follow

pleasure.

your

Co,, Inc.

is

to

A complete

alphabetical

index

appears

at the

end

of

this manual

WEIGHT

DIMENSIONS

Overall

Handlebar width

Ground

length

clearance

Wheelbase

Dry weight

AND

. . .

.....57.3in.(145.5cm)

Steeringangle.

Rake.

Trail .

Telescopic

Front suspension

Rear suspension

Fuel tank

Transmission

fork .

Frorrt

Model designationletter.

. . .

. .

8.9

. . . Swinging arm,

CAPACITIES

2.2

. . 7 oz.

ENGINE

(wet)

.2112

(212.5

in.

83.6

34.2in.

12

in.

233 lbs.

in.

. 5.5

oil dampened

(225

in.

mm)

oil dampened

US Gallons

pts.

each side

cm)

(87

cm)

(30.5

cm)

(105

Kg)

....45'

... . 30'

(140

mm)

travel

coil spring

(8.5

lt)

No reserve

(1200

(210

..

cc) cc)

MX

Type .

Bore .

Stroke

Piston

displacement

. . . .

Compressionratio

Fuel and

Lubrication

system

. . . .

Startersystem

IGNITION

Type . .

lgnition

Triggbr air

Spark Spark

Capacitor

timing

plug

gap

.

electrode

Discharge

. . . .

gap

CARBURETOR

Type.

Venturi dia . .

Mainjet

Lowspeedjet....

cycle,

2

2.835

2.346

..

3.590

Primarykickstarter

...

SYSTEM

DANSI or

(Dansi)

0.020 in.

.. Dell'Orto

..

single cYlinder

in.

(59.6

in.

1242.6

....11.8:1

mixture

oil

Motoplat

CDI

before

-

0.012

(0.40

-

0.50

(

PHM3SGS

1.496 in.

....189

....,..70

(72

mm) mm)

ccl

: 1

2O

TDC

0.016 in.

mm)

0'5

(38

mm)

2

www.ClassicCycles.org

Starting

Throttleslide

jet

...

.............

:..

Meteringpin..

Mainnozzle ....

f dfe mixture

screw setting .

Air filter Plastic

1

.....75

....K2

...260A8

1/2 turns

foam

element

open

Gearshiftpattern

Transmission Chain

type

sprocket

.

518

114

x

Harley-Davidson

Part

down

-4up

l

No.40000-77.M

TRANSMISSION

Clutch wet, multi Primary drive Primary Primary

Gear ratios:

drive

ratio .

Firstgear

Second

Third

Fourth

gear

gear.

gear

pinion clutch

gear

... :.....(1:1.928)...

.

,i. . . . . . .(1

.{. .r.

'i

..

SYSTEM

. ..:22teeth

..i...

..60teeth

....(1:1.555)...

:1.238)

(t

:1

.;

. )

. . .

.

Fifthgear.....

www.ClassicCycles.org

plate

2.727

14127

18/28

2't/26

21/21 23119

Frontwheel

Rear

wheel

Front

brake . . .

Rear

brake

Rims.

Spokes

pressure.

Tire

WHEELS

AND BRAKES

tire..

.

tire .

. internal expanding,

(0.i

psi

.. 10

....3.00x21

single

shoe type,

shoe type, i.d.

36/wheel,4

Kg/cm2

i.d. 140

)front

in.

leading

mm

140 mm

mm

dia.

and

rear

Throttle control

1.

Front brake

2.

Rear

3.

4.

brake

Kickstarter lever

control

pedal

grip

lever

-

Fig. 1

Right

www.ClassicCycles.org

side view

1.

Gearshift

2.

Clutch leyer

3.

Fuel valve

4.

Fuel

tank

lever

filler

cap

Fig. 2

-

Left

side

view

www.ClassicCycles.org

5_

Running in the

MX 250

The

Operate the

more

than

engine

This

without high

practice

erly. The

Motorcycle

requires a short breaking

motorcycle for

half

throttle.

RPM

will help

running-in should be

moving

the

Maintain light load or lugging.

parts

first hour using not

to break-in

performed

with new motorcycles, but also after

cylinder,

Fuel

The MX 250

gasoline-oil

a

correct

engine

Use

20

engine.

Use only

gasoline.

piston

and oil

oilquality and

damage.

high

a

:

1 is the coqrect

Premium Grade

,

andlor

recommendation

has a two-stroke

mixture

quality

piston

for

mixture ratio in order to avoid

SAE 30

gas

rings.

engine which requires

proper

lubrication. Use the

viscosity racing oil.

mixture ratio

to oil

(high

octane) leaded

period.

in

on the

prop-

not only

replacing

for

this

much

excessive

preignition.

Fuel

-

Always

Pour

and

sure the fuel

Do not

Remember

easily with

Use the oil-gas mixture within

oil

will cause spark

carbon

mixing

procedure

mix

the oil

shake thoroughly for

that the

tank.

mix vegetable

formation

gasoline

and the

fuel

is

and gasoline

properly

and mineral oils.

that vegetable oils

gasoline

mineral oils

as

oil in

a

plug

that

a clean

fouling

may lead

and

container.

into the container

few

minutes.

mixed, before

not mix

do

do.

few

a

filling

days.

to

Make

as

Too little

engine wear

oil

in

the mixture

possible

and

will cause

engine

severe

damage. Too

www.ClassicCycles.org

Transmission

premium

Use

a

engine

oil.

oil

quality

SAE

\0

W

-

40

or 20 W

-

50

Starting

-

When enrichment starter

grip.

starts.

when

-

When

mixture

throttle

starter

the engine

lever

sharply

Open the

Lower

the engine

the

the fuel

engine

enrichment

114

of

lever.

is

cold, raise

(A

-

fig.

without

throttle

mixture

warms

up.

is warm,

lever

a turn

the fuel

3). Push

valve

down

opening

when

enrichment

do

not

use

(fig.

4l'.

and operate

mixture

the kick-

the

throttle

the engine

lever

the fuel

Open

the

the kick

Fig.

-

3

Fuel

mixture

-

4

Fuel

mixture

enrichment

lever

-

OFF

ON

(open)

(closed)

www.ClassicCycles.org

G'earshift

five-speed

The

engage

To

from the

low and

shift

the

neutral,

between

travel

Engine

To

lever,

cycle.

tb

Turn

when

stop

start

as

stop

the

lever

gearbox

gear,

low

neutral

second

lever

push

position,

gear.

once

down

low and

button

engine,

the

no ignition

engine,

the

fuel tank

engine

is stoPPed.

operates

push

engage

To

for each

raise

or

second

just

switch

push

valve

the

which

the

operate

is

the

lever

as shown

gear

shift

located

is

higher

gear.

lever

gear.

the

fitted on

engine

"off"

the

to

fig.

in

lever

between

pull

gears,

To shift

half of

a

kickstarter

motor-

this

button.

stop

position,

5.

down

up

into

the

SHIFTING

TO

SEOUENCE

HIGHER

GEARS

NEUTRAL

-

suspension

Rear

spring

The

spacers

removing

rear

The

attempt

placed

8

preload

located

the

shock

disassemble

to

with

units

may

under

spring.

absorbers

new ones

be

the

cannot

them,

when

adjusted

upper

as they

damaged

spring

adjusted;

be

do

be

of

after

not

re-

out'

means

by

collar

must

or worn

www.ClassicCycles.org

SHIFTING

LOWER

TO

-

Fig. 5

SEOUENCE

GEARS

Shifter

Front

brake

Front

brake

lever free

the lever, should

Adjustment

justers,

(1

lever

the

cable

can

be

one of which

-

fig.

6) and the other at

(1

-

fig:

Fig.6-Brakeadju*er

travel, measured

be maintained

performed

is located

7).

at the

at 112

means

by

at the front

the lower end

tip of

to

314

of two

brake

in.

ad-

of

www.ClassicCycles.org

Rear brake

Rear

brake

pedal,

the

performed

are fitted

at

pedal

should be

end of

the

free travel, measured at the tip of

(fig.

8). Adjustments

adjusting nut

an

(fig.

9).

means of

by

the cable

one inch

(A)

Clutch

The

normal

(measured

performed

be

clutch

at the tip of the

by means of

and upper adjuster

free

lever

lever). Adjustments

loweradjuster

(2 -

tig. 11). lf the

travel is one-half

cannot be adjusted to the above clutch is

follows

not

operating correctly, adjust controls as

(see

fig. 10).

inch

can

(1

-

10)

fig.

free

travel

value or when

pedal

Fig. 8 - Brake

10

free travel

www.ClassicCycles.org

Fig.

-

Rear

brake

adiusting

9

nut

1. Remove access

cover screws

from right side crankcase.

2. See that

adjusted

Loosen

3.

screw

4. Loosen

screw inward

(screw

turn

lowest

Turn cable

5.

where all slack

handlever)

6. Adjust clutch

until clutch is

screw

eliminated

out play

juster

clutch

outward

cable

locknut on

(1)

locknut

and

turn

(A)

until it starts to

turns

farther inward.

position

harder). Then turn the screw one

on

adjuster

in

tighten locknut.

and

releasing engaged

inward until

(screw

1/8

and

at

turn to

handlever

establish slight release

retighten locknut

several

and access cover

adjuster

control

aCjuster

on release screw

(This

cam.).

(1)

cable

(screw

point

turns

for

1/2 in. handlever free

on left handlebar is

turns.

lower

coil

inward all

release

centers

back out to

is eliminated

screw

(B) turns easier).

where

harder),

then back screw

(A).

Adjust

adjusting

the

way.

(B)

and turn

clutch

the

position

play

in

at

release balls

the

(no

by backing off

Turn

play

free

bearing

free

cable ad-

play.

is

Minor

cable

adjustment

locknut and turning

handlever on

handlebar.

can be

knurled

made

loosening

by

nut located at clutch

www.ClassicCycles.org

Fig. 10 - Clutch

lower adjuster

Carburetor

The thrsttle

Adjustment

the carburetor

on

running

Slow

engine

idle,

tig. 12]l

the

stop

procedure

ing screw,

already

screw

inward

engine

screw

idles at

screwing

until the

11 Clutch

Fig.

cable

performed

be

can

caP.

adjustment

warmed

idle

the

until seated;

a

(B)

to

obtain

adiurter

upper

have a O.O2

must

the cable

with

should

up.

be

When engine

mixture adjusting

then screw

high speed.

or out

in

normal

Unscrewthethrottle-

normal

a

idle

the

idle is obtain€d.

in. free travel.

adjuster

with the

madb

is at

screw

until

out

it

Repeat the

idle..

mixture adjust

slow

(A -

Caution:

throttle

hold

s)ide.

Fig.

Before

partially

12-

Carburetor

adjusting

idle

open

adiustment

speed

prevent

to

screw

damage

inward,

to

12

www.ClassicCycles.org

Drive

chain

When the chain tension

2 3/4

a

in. free

midway between

must be clear of the

tensioner

(B)

(A)

while

play

on

the sprockets. The

ground,

must be disconnected

performing

this measurement

is

correct, there

lower run of

the

and

should the chain,

rear

the drive

from

the spring

(fig.

wheel

chain

13).

be

To

adjust the

wheel and

until

Always check wheel alignment

is made. Tighten axle

axle

turn both adjusting bolts

correct tension

drive

nut

tension, slacken the

chain

(C)

loosen then the

is

obtained

nut

securely.

rear

locknuts

(E)

an equal amount

(fig.

14).

after the adjustment

(D)

Fig. 13

-

Checking

chain tension

www.ClassicCycles.org

Fig. 14

-

Chaintension adjustment

13

Steering head

bearing

Support the crankcase on a

so that the

for

over-looseness by

fork leg

forwards. No

be

can

spannerwrench. Check

stop. There should be

to

front

wheel is

grasping

and attempting to

play

should be detected.

performed

by turning

Donot overtighten

for

over-tightness

by

no

wooden

clear

block or a stand

the

ground.

of

the bottom of each

move it

backwards

the head nut

the

turning

bind.

fork from

Check

and

Adjustments

with a

(fig.

nut

15).

stop

Swinging

Check swinging arm bushings

arm bushings

for

play

by

grasping

the swinging arm with one arm and the frame with

(refer

other

the

arm sideways;

No adjustment can be made; if

bushes

Wheel bearings

No side

as shown in

lf

14

ans spindle.

play

any

play

is

fig.

to

no

should

fig.

detected, replace

16). Try to move

side movement should be

felt

be

17),

necessary

the

at

wheel rim

the bearings.

the swinging

felt.

renew

(check

www.ClassicCycles.org

Fig.

15 - Checking

front fork

play

pressure

Tire

Too

high or

in order

Front: 10

Rear: 10

too low tire

to obtain

(0.7

psi

(0.7

psi

good

Kg/cm'?) Kg/cm'?

pressures

traction

)

must

be avoided

and long

tire li.fe.

Fig. 16

-

Checking swinging arm

play

www.ClassicCycles.org

Fig. 17

-

Checking

wheel bearing

play

15

lgnition

lgnition timing

The marks

be aligned

(Motoplat),

T.D.C.

Whenever

system

timing

should be checked

on the

as

when

(2.5

mm).

necessary, or if any

it is

been disassembled,

has

adjustment

DANSI: turn the

mm before

move

alignment.

T.D.C., then

pick-up

the

rotor and

fig.

in

the

follows:

as

crankshaft

plate

on the

18

{DANSI)

piston

is 0.100 in. before

perform

until the

slacken

to obtain

before

each

pick-up

or in

part

of the

the

piston

the screws

the correct

race.

should

fig. 19

C.D.l.

ignition

is

2.5

(A)

and

mark

A

special timing tool

is 0.100 in.

CDI System)

dealer.

t6

to indicate when

(2.5

mm)

before T"D.C.

(fig.

19 A) is available from

piston

(DANSI

your

www.ClassicCycles.org

Fig. 18

-

Checking

Dansi ignition timing

MOTOPLAT:

hold the base

screws

insert

rotor.

serted

that

2 mm

a

the

Turn into the

remove

in the

rotor

hole in the

mm

2

the

until

rotor and

plate.

hole

the

Refit the

(1

2 mm

base

slacken

rotor and

-

fig. 19) of

can be

plate.

the the

in-

Turn the

2.5 mm before

Check

holding tool

rotor and the base

piston

fitted in the

T.D.C.

position

means

by

spark

plate

plug

until the

of a dial

hole.

piston

gauge

is

Fig.

19

-

Checking

Motoplat

ignition

timing

www.ClassicCycles.org

A special

rotor

rotor. Contact

purchase.

dealer

for

Fig.

19

puller

your

-

Special

A

is needed to

local

Harley-Davidson

YA- 2266

tool

remove the

Transmission

The

transmission

races. Drain

the engine is

firmly.

it

with

transmission

The

amount

l12OO

Measure

fig.

cc). The

the

20) on

motorcycle

Insert

opening,

The

upper

the

dipstick until

but do

oil

level must

and lower

oil

must

the

transmission

warm. Refit

Refill

the transmission

(refer

oil

of oil

oil

level

the

to be added

level must

by means

transmission filler

standing

not

screw

always

level

marks

changed every

,be

oil

the drain

page

to

be

checked

of

up-right

the cap

be maintained

on the

thoroughly,

plug

and tighten

to

correct level

6).

is 2 1/8

every

the dipstick

plug,

with

on level

contacts

in.

dipstick

ground.

the filler

between

(fig.

two

while

pints

race.

(A

the

2'll.

-

Fig.

20

Oil dipstick

-

Fig.21

18

www.ClassicCycles.org

Oil level marks

on dipstick

Decarbonizing

Remove

the

cylinder head

and carefully remove

head,

cylinder

ful

not to

Decarbonizing

or

whenever it is necessary.

When

the

grease

the

Air

The

Wash

Soak

refitting

copper

to hold

head.

cleaner

air cleanerelementshould

the element

it in SAE

and refit

Gasoline plosive

well ventilated

not

smoke

when refueling

ports

scratch or

should

the

cylinder head,

gasket

correctly.

it in the right

in

30 motor

the element

is extremely

under

certain

area

or allow

or servicing

and

carbon from

and exhaust

damage

be

any

performed

Use a small

position

be

gasoline

and dry

oil; squeeze

in its

housing

flammable

conditions.

with engine

open flames

the cylinder

piston,

pipe.

Be very

part

of the engine.

everv

take

care

barrel

cylinder

care-

ten races

place

to

amount of

while fitting

cleaned every race.

it thoroughly.

out

excessoil

the

(ti1.

and

Refuel

stopped.

or

fuel

-

22

is ex-

in

Do

sparks

system.

23lr.

a

Fig.22

Fig.

23

-

Air cleaner housing

-

Air cleaner

element

www.ClassicCycles.org

valve

Fuel

Periodically disassemble

thoroughly

Another

ically cleaned,

clean

gauze

the

filter, that

is fitted in the carburetor.

fuel tank valve and

the

gauze

f

ilter with

should also be

solvent.

period--

Drive chain

Always

with a

wears

is

affected

rear

wheel.

Clean kerosene and

chain

is

strongly

Brake

Both

lubrication

keep the

high

rapidly

drive chain

quality

may even break;

and

and there

the chain

thoroughly

apply

lubricant containing

recommended.

lining

front and

rear brakes

inspection openings

thickness

Minimum

20

without

lining thickness:

removing the

properly

is less

lubricant.

power

chain

with a

lubricant.

the

molybdenum

are equipped

for checking

wheels

0.080 in.

lubricated

A

dry

its efficiency

also

available

solvent such

The use of a

disulfide

brake

ffig.

(2

mm).

www.ClassicCycles.org

chain

at the

with

linings

24!'.

as

-

Fig.24

Brake

inspection

openings

Front fork

Remove

type drain

Reinstall

21O

Recommended

the front

plugs

the drain

cc. of new fork

fork

filler

caps

and drain

plugs

oil

the

oil.

(A)

and fiil

(f

ig.

25).

oil: Harley-Davidson

and

each

fork

the

oil

screw-

leg

with

type B.

Spark

plug

The recommended

the

Champion N59G.

It

is installed

range for

Periodically electrode

justed

Specified

Spark

Replace

by

plug

the spark

as standard

average

remove

gap

with

carefully

plug

gap:

tightening

operating

spark

the spark

a wire

bending

0.020

in.

torque: 25tt

plug

every

plug

for

your

and is of the

conditions.

plug

and

gauge.

The

gap

the side

(0.5

mm).

-

lbs

3 races.

MX-250

right

measure

can be ad-

electrode.

is

heat

the

(3.5Kgm).

www.ClassicCycles.org

Fig.

25,- Front fork

drain

plug

21

Sometimes

different

heat range.

lf the spbrk

(whitish it with

insulator and

one of the

lf the spark

black,

When

insulator

the

the setting,

use a

the

shows a

The above buretor

properly

is

ture is used.

Final tuning

MX-250 is tuned

Your

factory.

you

field,

the spark

setting is correct, the

it may be

plug

advisable

tip shovrn

eroded

next colder

plug

hotter

heat range

remarks

adjusted,

is wet and the

tip

plug.

is correct,

light

brown

apply

and correct

for

However, depending

to modify the

have

may

plug

and

plug

to use a

of a

traces of overheating

electrodes),

range.

heat

replace

insulator

the spark

color.

plug

only when the car-

ignition

average

timing

gas-oil

mix-

conditions

on conditions

carburetor

final drive

the

ratio.

by

1. Carburetor assy.

Rubber connslor

2.

3. Clamp

Throttle slide

Slide spring

Meterinq

Clip, lllain nozzle

Screw

is

10. Cable adiuster

1 1. Locknut

12. Slide slop

13. Sprins

Enrichment assy.

15.

Screw

16.

17. Enrichment body

ldle mix. screw

18.

19. Sprins

washer

20.

Gasket

21.

22. Needle seat

Starrinq

23.

Low speed

24.

Float

25.

Float

26.

Float bowl

27.

Main

28.

Fitting,mainjet

29.

30. Fuel

31. Bolt

metering

ser compl.

ier

assy.

pivor pin

jer

filring

line

asry.

jer

nut

in

Carburetor

carburetor

The

Main

Low

jet:

speed

-

22

adjustment

standard

180

jet:

70

ietting

is as

follows:'

www.ClassicCycles.org

FiS.26

-

Dell'Orto carburetor exploded view

-

Metering

-

Throttle

-

Low

Carburetor

conditions tain maximu

A

visual

good

way

Switch

in top

cycle.

Remove

A

sooty,

pin:

slide:

speed

mixture

setting

(race

performance.

m

inspection

judge

to

the ignition

gear,

disengage

the

spark

black

insUlator

ture. A whitish

eroded electrodes,

The

spark

correct

plug

carburetor

insulator

K2

40

adjusting

should

field,

weather

of

the

carburetor

off

when running

the

plug

insulator

indicates

setting

nose

screw:

be adjusted

etc.) in

plug

spark

setting.

clutch

and inspect

nose

is light

and

indicates

nose,

a lean mixture.

is

obtained

bi.own.

1-j12

to

suit

order

insulator

full

at

stop

the motor-

the insulator.

a rich mix-

with

burned

when

turns

racing

to

ob-

is

throttle

or

the

a

Remember

opening

by

position

Between

justment

Low

air-fuel

page

tne

speed

2l..

the

metering

to obtain

to

is made

ratio

that

airffuel

obtain

314

mixture

from

between

mixture

pin position.

a richer

d'Jeaner

and

full throttle,

by changing

adjusting

idle

1/4

ratio

Raise

mixture;

mixture.

the

screw

to 1/4

gl4

and

is

affected

the needle

lower

the

mixture

jet.

main

regulates

throttle

mainly

the

(refer

clip

ad-

the

to

The spark

judging

for

heat

range

properly

gasoline/oil

adjusted

plug

readings

carburetor

is

correct,

mixture.

are an accurate

setting,

the ignition

and

when

using

means

plug

the

timing

the

correct

www.ClassicCycles.org

23

following checklist

The

helpful in.locating

will be

most

operating

troubles.

TROUBLE

not

will

Engine

Enginq overheats

does not

Engire

Clqtch slips

drags

Clutch

Carburetor

floods

start

run

smoothly;

loss of

power

CAUSE

1) The fuel tank is empry

2) The

3) The

4) The

fuel fuel

spark

5) The spark

6) lf there is

spark

valve is in the

tank tank breather is

plug

fouled

is

plug

damaged or dirty

is

no

spark

plug

lead end

clogged

when

held

trouble is in the ignition system.

1l lgnition timing

lmproper

2)

3) Cooling

is rbtarded

carburetor setting

fins clogged with mud

1) Clogged air cleaner element lmproper

2)

lean)

3)

Spark Worn

4)

Incorrect

1)

Worn

2)

carburetor. setting

plug

in bad condition

piston

and/or

clutch adjustment

plates

or weak springs

rings

1) Incorrect clutch adjustment

Transmission

2l

Float valve

1)

2)

Dirt or

its seat

3) Too

high float setting

other

too heavy

oil

and/or seat

worn or damaged

foreign material between

position

"off"

with carbon

cranking

near the

(mixture

engine

the

cylinder

is lean)

is too

float valve and

with

head,

rich

the

or too

24

www.ClassicCycles.org

After the

Spoke

Nuts and bolts

first hour of operation

nipples

.

Drivechain

After the

Transmission oil .

Each heat

first

two

hours of

operation

.......4.

Retighten Retighten

..'Retighten

Change

Sparkplug.

lgnitiontiming

Every

2 races

Piston rings Transmission

Every

Spark

Drive

chain

Throttle,

Gearbox sprocket

.

races

3

plug

.

clutch and

oil .

r.... Checkandclean

.., Check

Replace

chtrrge

Replace Replace

brake cables

Re*ptace

Replace

Spoke nipples tenslon . . Check

Drivechaintension. .... Check

Drivechain .... Lubricate

moving

Every

with oil and

Each

race

Transmission

filter

Air

Bolts

and nuts

part

of the

grease

oil level

motorcycle

.

Lubricate

Check

. Tighten

www.ClassicCycles.org

Every

5 races

Rearwheelsprocket,.......

Piston

Brake linings for

Every

10 races

Cylinder head,

Cylinder for wear

Carbon

from

expansion

...'... ...

wear

ports

piston

and

chamber

. . . Remove

Heplace

Replace

...

Check

Decarbonize

Check

Piston

(wear

Measure

skirt,

Piston

limit: 0.026 in.)

Piston ring

0.0045 in.

When

0.08 in.

ing rod must

Connecting rod

big end bearing

Crankshaft runout

Crankshaft Gear selector

(max

clearance

limit:

0.006 in.)

piston

right

at

ring

end

side

(wear

connecting

(

2

be

end

drum side

0.024

in.).

in

bore: 0.0016

diameter 25 mm from

angles to

gap:

piston pin

0.010

(fig.28).

clearance in

timit;

0.006)

rod

small end

(referto

mm)

replaced is supplied

and thrust washers.

with a new

must not

(axialplay):O.O12

float

play:

Perform this measurement

Perform

this measurement

+

0.0024 in. bottom of

axis

ffig.27l..

+

0.016

groove:

(fig.

in.

0.0025

29).

swing exceeds

fig.

30),

the connect-

one.

set

as a

with crankpin,

exceed

0.008

as shown in fig.

several

0.0015 in.

+0.024

+

0.016 in.

times,

www.ClassicCycles.org

(wear

in.

31.

+

Fig.28

Fig.27

-

Measuring

-

Measuring

piston

diameter

ring end

gap

Fig.

29 - Piston

ring

side clearance

Fig.

30

-

r-tl--

I

i)\.L6-

Checking

connecting rod

smal[

end

swing

Fig.

31

-

Measuring

gear

selector

drum

play

side

www.ClassicCycles.org

TOROUE Cylinder

Cylinder Clutch Primary CDI rotornut

SETTINGS

base nuts

head

socket head.bolts

hubnut

pinion

drive

..

Sparkplug.

.

18

. . . 11 ft-lbs

....70ft-lbs

nut

. . . 75 ft-lbs

,

.....,r ..-..5Sft-lbs

...25ft-lbs

ft-lbs

Page

Air cleaner

Garburetor . :..::::::::::::

Clutch

Decarbonizing Drive

chain

Front

brake .

Front fork

Fuel valve

lgnition

lnspection

Maintenance....

Maintenance

Operatinginstructions

Rear

timing

and adjustments

schedule

brake

.

.......

19

12-22

10 19

13-20

9-20

21

20

16

25

10-20

Rearsuspension...

Running-;6

plug

Spark

Starting Running

Instructions

Steering head Swinging Technical

Service spe.cif ications

9

Tirepressure......

Transmission

Troubleshooting.

7

Wheel

.

arm

data .

bearings

. : :: :::: :::: .

Stopping

and

bearing . . . .

bushings

oil

.. . : : : :. : : :

.

:: :

. .

: : :. : : :

....:

8

6

21

7 14 14

2

26

15

18

24

14

Harley Davidson MX 250 1978 Owner's manual

Specifications and Main Features

Frequently Asked Questions

User Manual