Small Engine Problems? Ask an Engine Mechanic for Answers ASAP
Start with your primer bulb. It has two nipples on it. When you push the primer bulb, one of those nipples produces positive pressure(push pressure) and when you release the primer bulb, the other nipple produces negative pressure(pull pressure/ vacuum). The way your primer works is it draws fuel through the carburetor rather than pushing it through. The fuel line that has the fuel filter on it inside the fuel tank will go to one of the two brass nipples on your carburetor. The correct orientation of the fuel lines on the carburetor is important, but if I have one that comes in to our shop for fuel lines and they are all rotted off like yours, I just have to pick one to put that first fuel line with the fuel filter on it, so pick one of the nipples on that carburetor, and keep it in mind for when all the fuel lines are hooked up. Next, the remaining nipple on your carburetor will have another fuel line on it, and that fuel line will go to the pull side(negative pressure/vacuum side) of your primer. You can determine which nipple on your primer is negative by placing a finger over the nipples and pushing and releasing the primer bulb. You'll feel positive and negative pressure respectively and that will tell you which one is the vacuum side. Apply that second fuel line from the remaining nipple on your carburetor to the negative pressure side of the primer. Next, the remaining nipple on the primer(positive pressure/push side) will hold the last fuel line, and it will go to the fuel tank via the second hole in the plastic case that goes to the fuel tank. This one is just a return line that feeds fuel back to the fuel tank via the positive pressure produced by that particular nipple on the primer. Now, you should be hooked up correctly, but I can tell you what symptoms you'll find if its not hooked up correctly(since we aren't sure if the initial fuel line we hooked up on the carburetor was right)...if its hooked up wrong, when you push the primer bulb, you'll see a ton of gas flooding through the throat of the carburetor. If you do find that this is happening, it means that the fuel lines on the nipples of the carburetor have been installed on the wrong nipples on the carburetor and the two fuel lines on the carburetor will need to be reversed...pull both fuel lines from the carburetor and switch each to the other nipple. Try to prime it again, and you should not see that same flooding.
I think this will get you straight, but if you have any more trouble, or you need anything else, please let me know.
Ok, if fuel floods out of the throat, then all you have to do is switch the two fuel lines on the carburetor....pull them loose at the carburetor and switch, or reverse them. I am attatching a couple of photos of a Poulan chainsaw. Its in our shop for repair, and the pictures are of the fuel line routing for reference. Switch the two fuel lines on your carburetor and that should straighten out your flooding problem.
I am not familiar with a Zama carburetor that uses so large a fuel line...3/32"-3/16" and .080"-.140" are what is typically used on your Mac. If your line sizes are in fact drastically different, you will likely have to change the respective fuel lines in order to compensate for the carburetor nipple size difference. Its a headache to do that, but if thats the case, it will just have to be done to get those lines swapped.
I am sorry to hear that. Please keep myself and Justanswer in mind if you need any help in the future.