Ah, Okay. That helps a ton. Way easier to figure out than the 1100
well obviously you need to look at it in steps. Since you know you have a problem with fuel not staying in the bowl I would focus on that.
it can only be going out the Power valve on the bottom or the accelerator pump on the side.
You could replace those items on your bench, fill the bowl and see if it holds the fuel or where it leaks from. Obviously if the bowl only goes half empty it is the accelerator pump. If it goes completely empty then the power valve is leaking or you have a crack.
One step at a time. You got this. These are super simple carbs, but they are old. There can be housing cracks. Faulty replacement parts. Make you pull your hair out.