EU2000i starting procedure that has worked really well for me ...
Run premium ethanol free gas treated with SeaFoam
Run Mobil 1 synth oil in the crankcase
Good plug, clean air filter, clean spark arrestor
To start - make sure the fuel cap vent is closed, turn on the choke, turn on the ignition switch, and let the generator sit for a couple of minutes - that allows any pressure that has built up in the fuel tank to force gas into the vacuum fuel pump. After a couple of minutes, start the generator, adjust the choke, and don't forget to open the fuel cap vent. Using this procedure mine have started almost every time on the first pull. :)