Honda UMK422 String Trimmer - GX22 Engine - Won't stay running

Hi all,
 
I just picked up this old non-running string trimmer and am hoping to get it back in shape. It will start and idle for a few seconds, and then quit. Also quits quickly or immediately on throttle.
 
I pulled it all apart and cleaned the carburetor, but it isn't the general bowl design I'm used to, instead it has two diaphragms. I'm guessing this is so it can operate inverted.. Symptoms were unchanged after cleaning and reassembling carb.
 
I saw on the parts listing that the primer button plate is called "air purge body" which got me thinking... When I press it, it pushes fuel back into the gas tank via a transparent line, but it also sends bubbles. Doesn't matter how much I prime, there's always bubbles. I checked to make sure the intake line was properly submerged in gas, and then swapped the lines to see if it was a pinhole. No dice, still air bubbles when priming.
 
I have a video of the priming, but I'm not sure how to post it here.
 
So I guess my question is, are the bubbles normal? This engine is so old, I'm surprised I haven't been able to find this issue thoroughly resolved on forums with some searching... It really does feel like the quality of Google results has just tanked recently...

Thank you for the troubleshooting help SRTsFZ6!
 
I bought oem replacement gaskets, diaphragms, and fuel lines and fuel filter. Installed them this morning and the engine acts the same It will start running and then quit on any throttle input. I tried starting with the choke on, and left it to idle, and it made it about four minutes, which is better than before at least.
 
My cellphone is broken currently, but I'll try to get some pictures of how I assembled the carb.

Thank you for the advice.
 
No adjustment screws whatsoever. I have the carb back apart now, and manually mapped out the passages with a squirt bottle, it looks like there are two gasket flaps that work as check valves, a piece of gasket diaphragm that acts as a pump based on the engine vacuum, and a third check valve directly below the main jet. The primer bulb pushes gas directly out of the return line, and then draws gas through the entire carb to reach it. Make sense there.
 
In the images:
1: flap check valves
2: diaphragm pump
3: main jet check valve
 
I still suspect the issue is an air leak, since air is being drawn in somewhere when I pump the primer bulb. After looking at the pieces above I thought it might be the main jet check valve malfunctioning, and allowing air to be sucked back down into the carb.
 
So I reassembled it, stuck the fuel lines into the tank, and pumped the bulb while holding the carb. Air bubbles appeared in the return line again and I could hear a gurgling sound during the bulb release, so I held my finger on top of the main jet's outlet up in the intake chamber. Still bubbles, still gurgling. Then I covered the small hole on the side of the carb that mates to the engine body to direct engine vacuum to the #2 diaphragm pump. No more bubbles, no more gurgles. The primer started just pumping gas through the system and the air was gone. Even after I uncovered the hole, it kept pumping gas and no more air bubbles appeared.
 
That would be great, BUT the vacuum hole just goes to the dry side of the diaphragm pump. There's no where for air to leak around it. It doesn't make any sense to me.
 
Edit: apologies, I'm split between two forums. Thank you again for pointing out the pump to me in the first response. I did buy new gaskets and diaphragms to rebuild the carb, the above was done using that.
 

Click on "open version" at the top, before you start typing.  
 
Nothing you posted since mine shows...."Approval pending"....
 
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