I have a new zdz50ng, which I was able to start today for the first time. I ran a tank through it on the ground without any problems. The next tank was supposed to be consumed in the air, and I filled her up. But when I was trying to start her again, I was only able to get it turning a couple of rounds before it died, and after a while she didn't want to ignite at all. I tried all different kinds of settings for the needles, the battery for ignition was fresh and the fuel system didn't breath air. Then I discovered that she didn't want to pump fuel, no matter how many times I flipped. Full throttle, choke closed and no air leaks in the system. I was puzzled by this, it was working fine just a couple of minutes earlier. When I got home, I dismounted the engine and attached another fuel line to the carb for a test. The fuel line is about 300mm and I connected the other end to a tank. With choke closed and full throttle, she wasn't able to pump any fuel through the line, but when I pressed my thumb against the small hole on the choke plate to seal it of completely, it suddenly started to pump fuel with a rate of approx. 2 inches for each crank. So, my question is: Shouldn't it manage to pump without me pressing my thumb against the choke plate? Is my only option to solder this hole? Is there something else that might cause this lack of performance when it comes to pumping fuel?

Be sure the choke plate is closing completely. Even the tiniest opening will cause a draw problem. You may solder the hole shut and drill a 1/32" hole in the solder.
Keep us posted.
Thanjks,