I also have a problem with "Hard to Start" on ZDZ50NG. I purchased this ZDZ from local presentative in Bangkok. I asked the owner where he ordered. It was came from Chezh Republic.
I choke the fuel and saw that there is fuel in the line and almost up to the carb. But I am not sure whether fuel got into the carb or not.

I fliped prop about 50 times and won't start. What I did to make engine start so far is as follows:-

1) Remove the plug.
2) Use hi-torque starter to turn the spinner several times.
3) Re-install the plug and then turn on Inigtion.
4) Flip prop about 3-4 times and engine starts.

So far I have to do this so many times and still cannot start engine by just turning the prop a few times like 3W or DA50.

I didn't take a look yet what carb number people mentioned in here since engine was already installed in the EDGE 540 Composite airplane./

Any comments throughly appreciated.