Pop off is the pressure it takes to unseat the needle. It is controlled by a spring and is critical to starting and low speed. it is checked with a pop off gauge. Mikuni makes a nice one. 0-100 psi is what I recommend. Pop off for the cv carbs I believe is 18psi. Check sbt for a kit. There really wasn't much of a kit offered for the cv carbs, but I think they had a wsm half kit I'll call it. Get the pop off gauge and test that before installing the kit, and I would NOT use the spring or needles in the kits. Just really use them for the gaskets and diaphragms. You can try the needles if you want, but the pop off must stay the same. Also check to make sure the return lines are not plugged. There should be a restrictor in the #3 carb before it goes to the tank, and make sure the return between carbs and the tank is not plugged. Pick ups in the tank have little filters on them. They can get plugged.