Do we know the new fuel is gasoline? Hopefully you had cleaned the tank and fuel line when you replaced the carb also. I have also seen the OHC's / OHV's develop a somewhat sticky valve to where they stick open due to varnish on the stem momentarily. Best to use carb spray rather than starting fluid, plus that can help to remove the deposits if that is the case. Beyond that, get a basic spark tester and watch when you have someone crank it over. A new plug isn't a bad idea either.

Sorry, it is a gcv160, not a gcx. Reposting.

I have a Troy-bilt gcv160 with a new carb. Will start with starting fluid and run high speed for a couple of seconds then dies out. It is getting plenty of new fuel, plug gets wet. Any ideas. Thanks.