Other possibilities:

When you say not hitting, do they run off a prime? Before hooking up the fuel system, make sure it runs a prime. If not, change the plug. Some oils used to store engines will ruin a plug.

Are you running with the needle too far open? Perhaps it is dieing rich. Close the needle and open just enough to pull fuel when choked.

Make sure the tank is low enough to not flood the engine. I would suggest top of tank at or below needle valve while on the bench.

I think everything else has been covered...except - make sure the new fuel has 20%-25% lube, preferably all or at least half castor for iron/steel engines. Many fuels used today are for large BB engines that do not need as much lube (~14%-18% synthetic).

George