Operation; F'onctionnemenl - Yamaha Towny MJ50 Service Manual

B.
Operation
1. WHEN THE KEY IN "START"' .•..•••
THE ENGI NE CAN
BE
STARTED.
When the main switch key is S(lt to
START,
the sta rt lndk:ator light
is turn·
ed on
by
the battery,
When
the
kick pedal is kicked, the fly.
wheel
magneto turns and the charge
coil
generatC$ a voltage of 150 to 350 volts
which is stored in the condcOS(lr in the
COi unit. When a
tri!l'J@r
voltage
from
the
pulser coil turns on the SCR l
!sili<:oo-controlled rectiller), the elect·
rtcity stored in the condenser is discharg·
cd
to
the
primary winding of
the
ignition
coll.
This induces a
high
voltage
su rge in
the
secondary winding ,,nd
produces a
spark across the spark p lug gap.
2. WHEN THE KICK PEDAL IS KICKED
WITH THE KEY IN "START" AND
THE THROTTLE GRIP IS OPENED .. .
THE ENGINE WILL NOT PICK UP
SPEED AND YOU CAN'T START OFF.
When the kic, k starter is k icked with the
key in
"'START" and
the throttle grip is
opened, the engine speed will increase
slowly. But before the
engine
reaches the
speed where the clutch engages, a trigger
voltage from the pulser coll
tums
on the
zener dioke (ZDI which 1urns on SCR2.
As a result, the voltage from the
charge
coil is not supplied to the
COi
unit; thus
no spark is produced al the spark p lug.
A• t he engine speed decreases, both ZD
and SCR2 t u rn off bu t
the
engine keeps
on
running by
ut il izi n~
the CO i
circuit.
By alternating the operation
specitied
above, the engine speed is controlled to
2,300 •
JOO
r/ min.
-2 -
B. fonctionnement
I.
QUAND L A CLE !OST SUR LA POSI-
TION START .... LE MOTEUR PEl!T
ETRE DEMARRE.
Qu311nd
I~ de
de comact
est
sur la posi·
tion STARl. le temoin "ST1\RT"' est
allum~
par
m<
hauerie.
Qu11.rtd la pedale de kick est
acrionn~c.
le
\Ohmt
m~~tique
coume
ct
tc
bobinage:
~
char:;• ginere une tension d e 150
a
350
'"<>Its
qui est stocket d•ns le con·
densoteur du bloc COi. Quand Un< teo·
sion de declenchemcn t vonant du
bobinagc d'impul<ions cnclenche kl SCR
(1hyristor). l"clectricit6 stockcc
dn1 "
le
condcnsateur est dcchargcc d•ns l"en-
roulc111 ent
primaire de la
bobine
d"ul·
lum:igc. Ced
induit
unc pointc
de
haute
tension d:ms l'c:uoulcmen1 sccondaire ec
cntrafnc le j>illissement d'unc
~Linc.<lte
cntn: lcs
electrodes
de la bougie.
1.
QUA'.\'D LA PEDALE DE KICK EST
ACl'IO!'\NEE L.ORSQLll:: LA CLE Of.
CONT,\CT EST SUR LA rosJTJON
START ET LA POIG'.'<EE D"AC("ELE·
RATION OUVERTE .... LE MOTEUR
:-<E l'REND P ... S 01:: Vll'ESSE ET
VOUS 'llf. POUVJ:2 PAS f'ARTI R.
Quand I< k ick est actionnc lorsquc la clc
de <'On tac t at sur la po:.ition ST A RT et
b poiin<c d
'a<..:<!loration
ou«rr~.
la
nh~~ du moteur augmcnte lcnrement.
..\vane
que c~ne \i l~>Se aueigne le
re,Pme
d'embrayate. UM
r~nsion
de
d~clenche·
mtnl ' cnant
du
bobinagc d"impulsions
cndcnchc la diode zencr (ZD) qui
cnclencbc le
SCR~.
Par snitc. la 1•nsion
du bobinage
d~
chaii:c n'cst P"" enYOyee
au bloc COi ct ii n'y a done pas de
iaiUl<sement d'<'tiocdlc cntre les
~lcetro·
des de la bougie. Quand la •itcs.c du
motcur diminue. la diode
z~ncr
(ZDJ ct
kl SCR2 sonL dedenches
amis le motcur
con tinue de tou mer gr3cc au
circuit
C.:01.
Par alternance des operations
s~cifiees
ci ~des.swt,
le regime du motcur est
main·
tcnu
~
2.300 • 300 tr/ mn.