MAGNETO
Magnetos on the
a r e e x t e r n a l , s e l f contained u n i t s which a r e flange mounted on the g e a r
housing and d r i v e n off the c a m g e a r .
Two b a s i c types of m a g n e t o s a r e u s e d . The s t a n d a r d m a g n e t o
(Wico Model
i s r e f e r r e d t o a s a s i m u l t a n e o u s f i r i n g magneto.
A
s p e c i a l r a d i o shielded s i m u l -
taneous f i r i n g m a g n e t o i s a l s o u s e d . T h i s type f i r e s both s p a r k plugs a t the s a m e i n s t a n t . Ignition
o c c u r s only in the c y l i n d e r in which the p i s t o n i s a t the ignition p o i n t - - t h e s p a r k in the o t h e r cylinder
i s ineffective s i n c e t h i s o c c u r s on the e x h a u s t s t r o k e .
The o t h e r m a g n e t o i s c l a s s i f i e d a s a d i s t r i b u t o r type magneto.
T h i s h a s a built in d i s t r i b u t o r
r o t o r which s w i t c h e s o r d i r e c t s the ignition voltage t o the p r o p e r s p a r k plug a t the a p p r o p r i a t e t i m e .
Two d i f f e r e n t d i s t r i b u t o r m a g n e t o s a r e u s e d . One i s the Wico Model XHG-2 and the o t h e r i s the
F a i r b a n k s - M o r s e M o d e l
The F a i r b a n k s - M o r s e
is
a r a d i o s h i e l d e d m a g n e t o which i s
u s e d m a i n l y on e l e c t r i c p l a n t a p p l i c a t i o n s w h e r e any high f r e q u e n c y e m i s s i o n m u s t be s u p p r e s s e d o r
contained. Since the s e r v i c e and t i m i n g p r o c e d u r e v a r i e s f o r e a c h m a g n e t o , e a c h i s c o v e r e d s e p a r a t e l y
i n this m a n u a l . S p e c i a l t o o l s and t e s t e q u i p m e n t a r e r e q u i r e d t o p r o p e r l y r e c o n d i t i o n m a g n e t o s . T h i s
w o r k should t h e r e f o r e b e done only a t a qualified m a g n e t o r e p a i r s t a t i o n .
M o s t m a g n e t o s u s e i m p u l s e couplings which function t o i n t e n s i f y the ignition s p a r k a t low s p e e d s
t o f a c i l i t a t e s t a r t i n g .
T h e i m p u l s e coupling functions a s a m e c h a n i c a l r e s e r v o i r t o s t o r e e n e r g y .
B a s i c a l l y the i m p u l s e coupling c o n s i s t s of a s h e l l and a hub connected t o g e t h e r b y a s t r o n g s p r i n g .
One half of the coupling ( t h e s h e l l ) i s f i t t e d t o a d r i v e m e m b e r on t h e engine d r i v e shaft. while the
o t h e r half (the hub) i s k e y e d t o the m a g n e t o r o t o r s h a f t . In o p e r a t i o n a t slow s p e e d s , a pawl on the
m a g n e t o half of the coupling e n g a g e s a s t o p pin mounted on the m a g n e t o f r a m e which a c t s t o p r e v e n t
f u r t h e r m o v e m e n t of the r o t o r while the engine half of the coupling
t o r o t a t e . The r e l a t i v e
change in position winds the connecting s p r i n g . When ignition s p a r k i s r e q u i r e d , the pawl i s r e l e a s e d
a n d the d r i v e s p r i n g p e r m i t t e d t o s n a p the m a g n e t o r o t o r f o r w a r d a t high s p e e d t h r o u g h i t s f i r i n g
As the s p e e d of the engine p i c k s up, the c e n t r i f u g a l f o r c e a c t i n g on the p a w l s withdraws
t h e m in a position w h e r e they no l o n g e r engage the coupling s t o p p i n a n d the i m p u l s e coupling then a c t s
a s a solid d r i v e m e m b e r .
S t a n d a r d Magneto ( W i c o XH-ZD): A f t e r e v e r y 500 h o u r s of o p e r a t i o n , r e m o v e end c a p and l u b r i c a t e
c a m wick with Rycon g r e a s e then c h e c k condition of b r e a k e r c o n t a c t s . If d i r t y , c l e a n with s o l v e n t
s u c h a s l a c q u e r t h i n n e r a n d a c o a r s e cloth. If a s l i g h t a m o u n t of m e t a l t r a n s f e r o r pitting i s noted,
d r e s s c o n t a c t s with e i t h e r a s m a l l t u n g s t e n f i l e o r a fine stone. Contact point gap m u s t be r e a d j u s t e d
a f t e r r e p l a c e m e n t o r p e r f o r m a n c e of a n y s e r v i c e on c o n t a c t s . U s e following p r o c e d u r e t o a d j u s t :
1.
T u r n engine o v e r by hand u n t i l points a r e wide open ( a t h i g h e s t point on c a m ) .
2.
L o o s e n t h e two c l a m p s c r e w s u n t i l c o n t a c t p l a t e c a n be moved.
3 .
I n s e r t b l a d e of s c r e w d r i v e r in adjusting slot and m o v e p l a t e until
.
015" m a x i m u m c l e a r a n c e
i s m e a s u r e d ( f e e l e r gauge) b e t w e e n c o n t a c t s . A f t e r p r o p e r gap i s a t t a i n e d , s e c u r e l y tighten
c l a m p s c r e w s t o l o c k p l a t e a t t h i s s e t t i n g .
I
I
FIGURE 6- 2
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TYPES
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K662 ENGINE
6.3
