Two things could be happening, from your description. The fuel pump may be able to provide decent volume, but what about pressure?It's possible that when clamping off the return line, you raised the pressure enough to keep the bowl full. The problem MAY be a stuck float still....if it is hanging, the extra pressure from the return line being clamped off could force the fuel on thru. The problem could also be the fuel pump itself.
Do you have a way to check the fuel pressure?

To get the accelerator linkage lever off the carb top, there is a TINY roll pin that goes thru it....take a small punch, or nail, and press the roll pin inward, toward the carb body. This will allow you to remove the linkage, and the top of the carb. When re-assembling it, you can use a small screwdriver to pry the roll pin back into the linkage lever.

No, I don't. How would you do that?


Thanks. I saw it, but I didn't dare to remove it because I was not sure I can insert it back in place, correctly.

You would need a fuel pressure gauge,and connect it after the fuel pump. You could remove the fuel line going into the carb, and connect it there. You'll be looking for at least 6psi under heavy throttle.

The roll pin, when pushed IN, will not go anywhere...it will bottom out against the carb choke housing...so it will not fall out, and get lost.

Thank you very much for the tip.