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Hesitates, or Bogs When Stepping on Gas

Carburetor technical help: hesitates, or bogs when hitting the accelerator

Hesitation or Bogging

When stepping on the gas, the engine needs a little extra gas before it gets to cruising, or power. When this gas is not available you will get a hesitation, or bogging. The may also include popping back through the carburetor.
While the electrical system can also cause this problem, we are going to concentrate on the fuel system only here.
1st thing you need to do is do a quick test of the accelerator pump circuit to see if the circuit is working.
One possibility you probably haven’t considered. Hesitation can be a result of using a carburetor not designed for the vehicle.

No Fuel Coming Out of the Main Discharge

You already did the quick accelerator pump test so now we need to get to the nitty gritty.
The instructions below may be a bit different depending on the type of carburetor.
  • Remove the carburetor from the engine.
  • Take the top off of the carburetor.
  • Fill the float bowl with a fluid like mineral spirits.
  • With the pump all the way down, lift it up to the top of the pump well. The pump well should fill with fluid.
    • The pump well doesn’t fill – If there is a check ball on the bottom of the pump well, then that is where the fluid fills. The suction of the pump going up and the weight of the fluid will lift the check ball and allow fuel to enter. For those that don’t use a check ball, the fuel will flow over the side of the pump well.
    • For those with the check ball check the passage from the fuel bowl to the pump well. You can do this by blowing compressed air into the pump well hole and test to see if air make it through to the fuel bowl.
  • Remove the venturi.
  • Now with the pump well full, push the accelerator pump to the bottom. There should be fuel coming out of the main discharge. Not fuel means there is a blockage in the passage from the pump well to the main discharge.
  • Install the venturi.
  • Fill the pump well with fluid and push the pump all the way to the bottom again. Fuel should squirt out of the venturi. If it doesn’t, then you have a plugged venturi.
  • Fluid squirts from the venturi?
    • Fill the float bowl with fluid and put the carburetor back together.
    • Pump the throttle a few times to see fluid is quirting out of the venturi. If not, then you have something wrong with the pump itself, or the pump stroke.
      • Make any adjustments to the pump stroke as set forth in the carburetor kit instructions.
Hesitation
Updated on 01/05/2021

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