ORIGINAL: BarracudaHockey
I have 3 of those and worked on a pile of them, thats not a normal problem, especially for a new engine.
Either the choke plate isn't seating (it doesn't need solder) or you have a plumbing problem.
+1
Also, I would confirm the diaphragm is correctly installed and not hardened
A maintenance kit is cheap from you local lawn mower shop and includes different types of diaphragms, gaskets etc