DCOEs have 5 fuel "phases". But, if you throttle plates return to
idle position, there should not be any above-idle RPM level. Are the
throttle plates closing all the way?
Back to the 5 phases, they are: cold starting device(choke), idle,
progression, acceleration, and normal phase.
Cold starting is the device on the top rear of the carb. It dumps
fuel in behind the throttle plates to richen the mixture for starting.
The idle circuits also feed fuel behind the throttle plate.
The progression circuits are exposed as teh throttle plate opens. As
the plate opens the progression holes go from seeing pressure to
seeing vacuum and feed fuel.
The normal circuits feed fuel through the auxillary venturi.
The accelerator pump squirts a jet of fuel to compensate for sudden
large openings of the throttle.
To work properly, all fuel feeds and vents must be open. The thing
should drop from any RPM to idle when the plates are closed almost
instantly. Even if a fuel circuit sees abmormal pressure or vacuum,
forcing fuel into the airway, the throttle plates should be closed and
restricting the air so you would get a flooded state but not a high
RPM state.
I'd look closely at the throttle plates and throttle shaft seals. To
go above idle RPM it must have air and fuel. Where/how can it get air
and fuel in the proper ratios?
I'm sure Frank knows this stuff. I'm mostly writing to get it
straight in my head and for others who may be interested in the DCOE
and Frank's Woes.
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