TURNS OPEN
FIGURE
--
ADJUSTMENTS. DOWNDRAFT CARBURETOR MODELS 28
228,
ENGINES
S T E P
-
F a r p r e l i m i n a r y a d j u s t m e n t , t u r n Main F u e l needle
3
t u r n s i n a c o u n t e r c l o c k w i s e d i r e c t i o n ,
t u r n Idle F u e l n e e d l e
in a
S T E P 3
S t a r t e n g i n e and o p e r a t e a t n o r m a l s p e e d until n o r m a l o p e r a t i n g t e m p e r a t u r e s a r e r e a c h e d .
S T E P
4
Main F u e l A d j u s t m e n t
-
With engine o p e r a t i n g a t f u l l t h r o t t l e and full l o a d , t u r n Main F u e l
Needle in ( c l o c k w i s e ) u n t i l engine s l o w s down ( l e a n ) , note p o s i t i o n of s c r e w , then t u r n needle
u n t i l engine r e g a i n s s p e e d and t h e n a g a i n s l o w s down ( o v e r r i c h ) .
T u r n n e e d l e b a c k in until i t i s p o s i t i o n e d halfway b e t w e e n l e a n and
s e t t i n g s . If
a d j u s t e d p r o p e r l y , the engine should a c c e l e r a t e s m o o t h l y a n d o p e r a t e with s t e a d y g o v e r n o r
a c t i o n .
S T E P
5
-
Idle F u e l A d j u s t m e n t
O p e r a t e engine a t idle s p e e d of a b o u t
R P M ( a d j u s t Idle Speed
s c r e w u n t i l t h i s s p e e d i s a t t a i n e d
c h e c k with t a c h o m e t e r ) . T u r n Idle F u e l Needle in
( c l o c k w i s e ) u n t i l engine s l o w s down and idles r o u g h t h e n t u r n s c r e w out until engine s p e e d s
up and i d l e s s m o o t h l y a t the d e s i r e d idle s p e e d .
S T E P
6
F i n a l A d j u s t m e n t
-
Since m a i n f u e l and idle f u e l a d j u s t m e n t have s o m e e f f e c t on e a c h o t h e r ,
r e c h e c k e n g i n e and m a k e f i n a l a d j u s t m e n t s a s n e c e s s a r y t o a c h i e v e s m o o t h e s t operation.
NOTE:
If the p r e c e d i n g s t e p s d o not r e m e d y p r o b l e m s a t t r i b u t e d t o c a r b u r e t o r , c a r b u r e t o r r e c o n -
ditioning m a y b e n e c e s s a r y .
C a r b u r e t o r Reconditioning: H a r d s t a r t i n g , l o s s of power and r o u g h i d l e a r e s o m e of the p r o b l e m s t h a t
c a n b e a t t r i b u t e d t o i m p r o p e r a d j u s t m e n t o r d i r t , gum o r v a r n i s h d e p o s i t s within the c a r b u r e t o r . If a
p r o b l e m s t i l l e x i s t s a f t e r c a r b u r e t o r i s r e a d j u s t e d , the c a r b u r e t o r should b e d i s a s s e m b l e d and t h o r -
oughly c l e a n e d .
T h i s should a l s o b e done a s a r e g u l a r p r e - s e a s o n s e r v i c e a f t e r engine h a s been
s t o r e d f o r a c o n s i d e r a b l e l e n g t h of t i m e .
All p a r t s s h o u l d be c l e a n e d in s o l v e n t . Gum i s e a s i l y r e m o v e d with a l c o h o l o r a c e t o n e solvent.
B e s u r e c a r b o n d e p o s i t s a r e r e m o v e d f r o m b o r e e s p e c i a l l y i n a r e a w h e r e t h r o t t l e p l a t e s e a t s in c a s t -
ing. Blow out a l l p a s s a g e s with c o m p r e s s e d a i r . DO NOT u s e w i r e b r u s h o r d r i l l t o c l e a n out j e t s .
R e p l a c e a l l worn a n d d a m a g e d p a r t s . Always u s e new g a s k e t s . C a r b u r e t o r r e p a i r k i t s a r e a v a i l a b l e
f o r m o s t c a r b u r e t o r s - - k i t s include bowl nut g a s k e t s (when r e q u i r e d ) howl r i n g g a s k e t , f l o a t pin, bowl
baffle g a s k e t , a n d f u e l inlet n e e d l e and s e a t .
