Thread: What causes low rpm hesitation?

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its possible there is too much gas dumping in to the cyls. that can happen @ low rpms from a stop, especially w/ double pumpers i've read, because so many guys bolt em on cause they are great for a really built motor, so yeah, check the metering rods, maybe get some smaller ones?

Do a compression test on the motor. Also remove one of the valve covers and see that all the valves are opening as they should. The cam could be going soft.

You may want to check your fuel filter. Dirt in carb will bring this on.

I did a compression test and they were all between 169 and 177, checked all the valves and they are all opening fine. I took the carb off and there was some dirt in the left bowl, soaked it overnight, blew it all out. It is better but still there just not as extreme. Runs fine cruising but has dull accelleration after feathering it through the dead spot. The two metering rods control fuel flow during accelleration or all the time? Could it be timing, say needing different advance wieghts in the distributor? Advance to timing a touch? I moved the linkage on the accelerator pump arm up to the top and no difference so I put it back in the center. Could the front 2 adjustable jets have anything to do with it? Also inside my exhaust pipe is pitch black soot, to rich huh?

The metering rods are hooked to a piston that raises them out of the jets upon acceleration. If they are in any kind of a bind you would run lean until they pop out of the jets. I've also seen the rubber on the accelerator pump roll up a bit to where you don't get a full shot. There is also a tapered check valve in the primary discharge circuit that could be sticking.

Check and see if the accel pump is giving a healthy shot of fuel with the engine turned off and your head over the carb with the filter off, if its a weak shot.. try putting in a new accel pump. Could also be your mixture is off? Just a couple thoughts since I've experienced the hesitation blues for about 3-4 months until i figured it out.