Yamaha RD250 Owner's Manual page 124

2 3 . S p a r k p l u g
T h e s p a r k p l u g in y o u r m a c h i n e c a n teil y o u a g r e a t
d e a l as to h o w t h e e n g i n e is o p e r a t i n g w h e n y o u k n o w
h o w to " r e a d " t h e p l u g . If the e n g i n e is o p e r a t i n g
c o r r e c t l y , a n d if it is b e i n g r i d d e n c o r r e c t l y , t h e n the tip
of t h e w h i t e i n s u l a t o r in the s p a r k plut w i l l be a light
t a n c o l o r . If, w h e n y o u r e m o v e the s p a r k p l u g , it is
v e r y d a r k b r o w n or b l a c k , t h e n a p l u g w i t h a hotter
heat r ä n g e m i g h t be n e e d e d . T h i s S i t u a t i o n is quite
c o m m o n d u r i n g t h e e n g i n e b r e a k - i n p e r i o d . If the
i n s u l a t o r tip s h o w s a very light t a n c o l o r , or is a c t u a l l y
w h i t e , or if the e l e c t r o d e s b e g i n to m e l t , t h e n a s p a r k
p l u g w i t h a c o l d e r h e a t ränge is r e q u i r e d . A g a i n , if the
s p a r k p l u g i n s u l a t o r tip d o e s not h a v e a light tan c o l o r ,
h a v e y o u r d e a l e r i n s t a l l a s p a r k p l u g w i t h a different
heat r ä n g e to c o r r e c t t h e S i t u a t i o n . D o not a t t e m p t to
e x p e r i m e n t w i t h different h e a t r ä n g e s p a r k p l u g s y o u r -
self, a s it t a k e s a n e x p e r i e n c e d e y e to g a u g e w h i c h
s p a r k p l u g to u s e , a n d to g a u g e it t h e s p a r k p l u g is
a c t u a l l y at fault. It is all right t h o u g h for y o u to r e p l a c e
t h e S t a n d a r d p l u g . E n g i n e c o n d i t i o n s c a n c a u s e a n y
s p a r k p l u g to s l o w l y b r e a k d o w n . If d e p o s i t s b e g i n to
b u i l d up, or if the e l e c t r o d e s finally b e c o m e t o o w o r n ,
or if for a n y r e a s o n y o u b e l i e v e t h e s p a r k p l u g to not
be f u n c t i o n i n g c o r r e c t l y , r e p l a c e it B e s u r e , w h e n
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