85 720 Fuel problem

Hi all, back again with a question. I had the carb that would fill up and start to push out the accelerator pump housing. This started after I replaced the input fuel line.I installed a fuel hose from the pump to the metal line coming down from the carb. I tried the sugestion to block the fuel line and run the bowl down a few times and try to dislodge a possible piece of junk between the needle and seat. I can run at idle for a long time and no problem, but as soon as I try to run down the street 1 mile it fills up and starts to run bad. Once I ran it for 20 minutes around town with no problems, but the next day it was back to problem. I am going to take the front panel with the sight glass off and look in and see if anything could be wrong. My question; After getting access, what can I look out for. My Nissan service manual only gives me a diagram of the float section and exploded parts diagram of the carb. Thanks again, Jerry