Varnish in the bowl tells me that the carb may be new but someone has left it sit with gas in it. If the main jet has varnish in it, then the engine will starve for fuel when you open the throttle. Seafoam MIGHT help but soaking the dismantled carb in true carb cleaner, rodding out the passages with fine wire, washing in clear solvent and blowing compressed air through the passages may be your only solution barring finding another carb off a donor engine to try out.
Presumably, this is an I/C vertical engine you have.
Presumably, this is an I/C vertical engine you have.
