Notes and adjustments for IDF and DCOE Carburetors
All adjustment procedures are the same as the progressive
carbs. It is important to understand the dynamic differences of the two
carb styles Progressive and Synchronous carbs Or better described as
individual runner carbs.
The progressive idles through barrel and one mixture screw
hole, then transitions to a secondary barrel with an additional Idle / low
speed jet. The Individual Runner carbs IDF and DCOE have individual Idle
jets and mixture screws for each barrel. They also have an additional air
bleed screw and lock nut. This is not used for Idle adjustment or Idle
quality. The settings for this screw should be closed.
The Main adjustments Speed and Mixture Screw for the
individual runner carbs have different values than the Progressive. They
tend to be ½ of those used on the progressive
Standard IDF & DCOE Settings
Speed screw ¼
to ½ turn in after contact with lever.
Mixture Screw 1
turn out from seated
Follow the same basic procedures as used with the
progressive carbs with the exception that there is no choke system and no
need to clear the choke cam.
It is important to be very sure there is no throttle shaft
bind or over tightened levers. This is the number one reason for most
adjustment and tuning problems.
The rules of thumb still hold true
the base line settings are only the starting point. The example
If your mixture screw is out more than one turn like 11/2
turns then your idle jet is too lean go up one half size on the Idle jet
not main jet.
If you mixture screw is not out one full turn something
like only 1/2 turn out from seat then your Idle jet is too rich. This is
all based on the important fact
that your speed screws are not open
more than ½ turn if they are then that is also an indication that you
have a lean Idle circuit. You are cheating by opening the throttle plates
and exposing additional progression holes in the transition.
These carbs are also commonly used in pairs, this makes the
synchronization important please be sure when ever balancing twin carbs to
bring the high carb down to the low carburetor.