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1926 Dodge brothers screen side truck starting running issues


Michael w

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Truck will start and run smoothly for 30 to 45 seconds then either shut off or if you accelerate well attempt to run but smokes and skips and jumps. Have cleaned the float and needle valve. Fuel is good. Plenty of fuel in the float tank. What should I do?

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Assuming you are using the vacuum tank and not a fuel pump, my initial guess would be that you might have a fuel/air ratio problem (too rich).  Is the smoke black?  It could be that the dashpot in carburetor is stuck or sticking.  Had the truck been sitting for a long time since last run?

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Here is a cross section of the carb.  The air valve is connected to the dashpot and the pair actually moves upward when air flow increases (it is shown in the down position at low throttle condition).  You certainly can try some carb cleaner shot in the air intake but if it's like my '25 set up, that will be hard to do without removing the carb from the intake bulb.  If the air valve/dashpot sticks in the up position, fuel metering will be too rich at low throttle setting.  The tapered metering pin regulates the amount of fuel going into the air by controlling the fuel flow area between the pin and metering orifice (main jet).  Think of a tapered pin going into a donut hole.  Depending on the relative axial position of hole and pin, the area between hole and pin (annulus) will change.  As the air valve rises, the metering orifice rises relative to the pin, letting more fuel flow.  The idea is to try and keep the fuel/air ratio constant for different throttle settings.

Stuart Carb cross sect..jpg

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