Quote:
Originally Posted by speeder
I have a general question about float level or fuel levels in float bowls of carbs; I know that if the fuel level is too low in the extreme, the engine will [B]starve for fuel under full throttle acceleration and if it's too high in the extreme, it will overflow and go places it's not supposed to go(?)
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(I'm talking out of my layman arse here...but I was under the impression: )
There is a float with a cutoff needle fill valve which always keeps the bowl level within range specs.
-The air-filled floats will crack and sink which allow the bowl to fill up completely.
-Fuel pumps usually have an internal delivery pressure regulator, but if the delivery pressure is too high it will overpower the needle valve cutoff and also flood the engine.
The main jet mostly regulates the fuel flow into the venturi where suction pulls it into the air stream to swirl and particalize.
-More swirl and turbulence makes a better mixture when warm, at a a loss of top end.
-More swirl and turbulence makes a worse mixture, when cold when it gels to the cold sides and carburetor heat is needed.
Under WOT/full acceleration, an extra long squirt of gas is pumped directly into the middle of the carb by the accelerator pump.
More gas=rich mixture=less chance of lean detonation under full load.
Idle -vs- under normal operation -vs- under WOT/full load are different things to a carburator.
A bad idle doesn't necessary mean bad operation, unless there are other mechanical faults of the engine.
Idle is controlled by the butterfly valve closing completely, where a separate bypass keeps the air moving faster and the fuel pulled into that limited but very fast-moving airflow.
-A notch in the butterfly allows some bypass air.
-A smaller separate bypass channel is controlled by an idle-air+idle-mixture screw.
-Those passages are smaller, so EGR waste and/or particles will block them up easily.