There is a part on the carb that looks like an accelerator pump. This is on a CH25 horizontal engine. I would check that and clean the carb out.
Are you sure fuel is being pumped into the carb bowl? Put fuel line from fuel pump to carb in a plastic bottle. Crank engine. It should be pumping fuel.
If you have two gas tanks, make sure both tanks have some gas in them. If the transfer valve is faulty, air will be introduced intot he fuel system.