[SEL] carb_fueling problem

[Clint D]

I have a Kohler CH18S engine, 18 HP V twin

when I start it, it will run a few minutes then run out of gas, seems that the
needle seat was sticking closed and not allowing fuel in so I pulled the carb,
cleaned very well, installed a kit, new needle valve etc.
I am running an electric fuel pump.

Afetr I rebuilt the carb, it started and run fine but may do so far 2 minutes or
30 minutes?? then will run out of gas. I can peck on the carb and it will run
again for no telling how long, yesterday I could not keep it from doing this when
I started it up and stood there and tapped on the carb every 15 seconds or so as
that is how long it wanted to run, it would stay runing as long as I done that,
then it leveled out and started running on its own but would run about 10-15
seconds and start acting like running out of gas but would pick up on its own ,
finally I walked off from it running and it came vack in 20 minutes it had died, I
tapped on the carb and started it up, then it ran all afternoon, about 4 hours

what could be the cause of this and what can I check out or try to do?

the carb is very clean inside?

Clint