Yamaha LB50IIAC User manual

YAMAHA

4RP-28197-20

EBOOOOOO

LB50 II AC/LBBO II

SERVICE

MANUAL

Yamaha

Motor

Co., Ltd.

First

edition,

March

1997

All

rights

reserved.

Any

reproduction

unauthorized

use

without

the

written

permission

Yamaha

Motor

Co., Ltd.

is expressly

prohibited.

INDEX

GENERAL

INFORMATION

PERIODIC

INSPECTIONS

AND

ADJUSTMENTS

ENGINE

OVERHAUL

CARBURETION

CHASSIS

ELECTRICAL

APPENDICES

CHAPTER

GENERAL

INFORMATION

FEATURES .......................................................................................................................1

MACHINE IDENTIFICATION............................................................................................5

EXTERNAL

VIEW

.............................................................................................................6

SPECIFICATIONS.............................................................................................................8

GENERAL SPECIFICATIONS...................................................................................8

MAINTENANCE

SPECIFICATIONS.......................................................................

GENERAL TORQUE SPECIFICATIONS.........................................................................

CABLE ROUTING...........................................................................................................20

SPECIAL TOOLS ............................................................................................................

CHAPTER

GENERAL

INFORMATION

FEATURES

Automatic

mechanism

Using a pair

shoe-type

centrifugal

clutches.

the

drive ratio is changed automatically.

@-------'

©-----~

1st

drive gear 9. Spring 16.

low

range

2. Clutch housing 10:

2nd

drive gear 17. High range

1st

clutch 11.

Shift

rod 18. Drive axle

2nd

clutch 12.

Main

axle 19. 1st driven gear

One-way

clutch

13. One-way clutch

Spring

6 Crankshaft

2nd

driven gear 21. Kick gear

Shift

lever 15. Sprocket

Kick crank

8. Kick pinion

- 1-

2. The use

automatic

2-speed

centrifugal

clutch

relieves

the

rider

from

the

cumbersome

operation

the

shift

lever.

That

is, ease

operation

and

additional

safety are ensured for

the

rider.

When

starting out,

gears

are

automatically

shifted

into

first, and

then

into

second

according

engine load. This

will

result in a

longer

life

the

engine.

Automatic

transmission

mechanism

The

automatic

transmission

mechanism

consists

two

shoe-type

centrifugal

clutches.

1st

gear clutch:

FGr

starting

out

and for

1st

gear operation.

2nd

gear

clutch:

For

automatic

change

2nd

gear.

Each

clutch

has

three

clutch

shoes

operated

centrifugal

force. These

shoes are

well

balanced

minimize

the

vibration

for

smooth

operation.

This clutch is

provided

with

linings

high

wear-resistance. and

thus

excellent

clutching

power

is guaranteed. The

heat

generated

friction

between

shoes and lining is

quickly

dissipated

through

the

gear oil

the

clutch

hous-

ing,

with

which

the

clutch

shoes are in

contact.

2. The

2nd

gear side is

provided

with

overrunning

clutch.

overrunning

clutch

for

starting

built

the

hub

driven gear

Longer

life is ensured

simple

construction.

1st clutch

2nd

clutch

1st

driven

gear

-2-

Theory

operation

Idling

idling, the 1st

gear

side

clutch

driven

by the crankshaft is

kept

uncoupled

spring force, because

the centrifugal

force exerted on

the

weights.

Starting

out

with

1st

gear

the

throttle

grip is

twisted

open,

the

engine speed increases, and the spring

force is

overcome

by the centrifugal

force, and

the

clutch

shoes are forced

against

the

clutch housing, causing fric-

tion. As

the

friction

increases,

the

tur-

ning force

the engine is

transmitted

the main axle

through

1st

drive and

driven gears.

3. Reduction and

2nd

gear

the

throttle

grip

further

opened,

the

2nd

side clutch begins

operate.

That is,

the

clutch shoes are forced

against

the

clutch

housing by

the

weights, and thus

the

engine

power

transmitted

through

2nd

drive and

driven gears

the

main axle.

this stage, the

1st

gear side clutch is

released because

is an

overrunning

clutch.

-3-

Clutch housing

1st

dutch

2nd

clutch

1st

drive

gear

1st

driven

gear

Subtransmission

Rear wheel

(j)

2nd

drive

gear

2nd

driven gear

8. Main axle

One-way

dutch

_---1-1-----=-.l-l-

Subtransmission

2. Rear

wheel

Sub-transmission

mechanism

order

increase the engine

torque

required

for

climbing

a hill

with

ease,

this

motorbike

is equipped

with

subtransmission.

Operation

the lever

D-range:

Driving on level roads

N-range:

Neutral (Engine

warming

up)

L-range:

Climbing

a steep slope

NOTE:-----------

The

shift

lever

must

be operated at

idling.

2. In

order

change

the

"L"

range,

first push

down

the

stopper

lever

and

then

set the

shift

lever

"L".

Kick

starter

mechanism

Both kick idle gear and

kick

pinion are

helically meshed.

When

kicked,

thrust

is exerted on the pinion,

thus

causing

move

off

the drive axle.

When

the

kick crank returns

its

home

position

after

the engine is started, the

kick

pinion

is forced back by

the

return

spring.

Dock

Main

axle

Driven

gear

4. Drive axle

1 One

way

clutch

Main

axle

Drive

axle

Ratchet

wheel

5 Kick crank

-4-

5 Drive range

6 Low range

Sprocket

8. Shift rod

@ ® ©

~I/

6 Kick

gear

7 Kick idle gear

Dock

Driven

gear

MACHINE

IDENTIFICATION

The

frame

serial

number

located

the

right-hand

side

the

headstock

assembly.

The

first

three

digits

identify

the

model.

This

followed

a dash. The

remaining

digits

identify

the

production

number

the

unit.

The engine serial

number

located

on a rais-

ed boss

the

upper

front,

left-hand

side

the

engine. Engine

identification

follows

the

same

code

frame

identification.

Normally,

both

serial

numbers

are

identical;

however,

occasion

they

may

two

three

numbers

off.

Starting

Serial

Number

439-1000101 (LB50 II AC)

34H-010101 (LB80 II AC)

Frame serial number

Engine serial number

-5-

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