18hp Cushman Haulster ('77) - rough runner

[nedlyped]

Hoping someone can advise:

Picked this 18hp '77 Cushman Haulster (898409-7710) up, wasn't running, spark plugs were fouled black. Replaced the intake manifold, cleaned the carburetor (Keihin ) including the passage way to accelerator pump, checked all lines, and replaced old fuel filter. Changed all the oils and oil filter. New spark plugs, checked coils, points filed and corrected, timing on. Air filter is a little dirty, but seems ok. I am getting a new one just in case though.

Now it runs, BUT it runs kind of roughly. Accelerates with a lot of power, idles well. However, sometimes it cuts out, esp. in 1st gear it seems to hesitate. I have to give it a lot of gas to get going (and it takes off!). Or tap/pump the gas pedal a bit to get it moving. Is there something I am missing for a smoother take off?

Carb, not sure of model number, I can only see markings "EDL 27" on carb? I know it is Keihin from images and that it only has a throttle stop screw and low-speed idle.

Should also note, previous owner added an electronic fuel pump, bypassing old mechanical one. A Yoneda universal one, not anything fancy - 12v, Output Pressure 2.5-4PSI, Pressure 0.028 - 0.045 MPA. It works, I can hear it churning, fuel runs through the system. Filter was originally set AFTER the pump and that's where I put it when I got a new gas filter. I read somewhere it should be BEFORE the pump, but that seems minor?

Help or advice appreciated.

Thank you.