CM450 carb problems

its an 1984 honda cm450e. it has VB22 carbs (CV) I'm having
hesitation/stuttering at about 1/4 to 1/2 throttle. the carbs have
been professionally cleaned and synced. the slides move easily
in the bore. once past this "stuttering" it runs fine. i just had
the carbs apart again to doublecheck and couldn't find any dirt in the
jets. these aren't the original carbs for the bike but every jet
has been properly sized as per the service manual. what am i
missing?? thanks.

 

Weak spark.

Ed Cregger

 

spark fat and blue, new plugs, coils measure fine.

 

1. Incorrect idle mixture screw adjustment. If the idle mixture screw is

checked the plugs, the tips are light gray in color and the insulator
is a very light brown. .

 

#
The plugs will clean up ok if it's only fouling occasionally. You'd need to
drive the bike for a while at the throttle opening that's causing the
problem and them stop and check plugs.
John.