I’ve got a clone gx390 13 hp generator. The carb developed a leak. I replaced it and now I can’t get it to start. I thought the first replacement carb might have been bad so sent it back and ordered another one. Same problem. I can sometimes get it started by forcing the throttle to minimum and holding it there. Then if I open it slowly it will run at speed for a bit then stumble and start surging and backfiring. The governor seems to be working okay. But when the engine is off, governor forces WOT. Is that normal? That seems to be causing the hard start problem. Not sure what is making it stumble at speed.
This is really frustrating, since it ran okay before swapping the carb. Heeeelllp!

WOT at throttle when off is normal.
 
There's likely a fuel filter inside the tank where the hose connects.
 
I would turn the fuel off first and remove the fuel at the carb (or valve)
Turn the fuel back on and look for proper fuel flow.  
 
Surging would occur with a "little fuel" flow issue.
 
I suspect that's your issue
And crap got into your old carb and stuck the float open. That would cause the leak to occur with the over flow of fuel.
 
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