No..no...no.... you don't get 240 volts by "linking up" two 120 volt generators. You get twice the power. Or put another way .. twice the current.... but all at 120 volts.
And also.... you don't need gasoline. There are plenty of kits to convert to propane or natural gas. Hutchmountain is absolutely the best. They are not "one size fits all" but are made specifically for those Honda units.
https://www.hutchmountain.com/
Note @Old Ridge Runner
IMHO. . Those EU2200s are the best quality and easy to move around. The conversion kits by hutch mountain are well made and easy to install.
Alternatively... you could get a Westinghouse IGEN4500DF (dual fuel) to provide the same power as two of the Honda EU2200s plus it's electric start and they already made it to accept gasoline or propane with a turn of a knob. I think the Hondas are probably better made (which is why I have two) but the Westinghouse IGEN4600DF has been running just fine. Propane is safer to store than gasoline.
I also have three of a cheaper brand.... WEN. There are plenty of these 79cc engine clones. (as opposed to those 120cc Hondas). Some of those 79cc generators may be superior to WEN. I don't know. I picked WEN because they sell parts on the website. But quality is so important in an outage, I look at my Hondas as the real survival gear. STILL... my TEOTWAWKI survival philosophy is heavily weighted in favor of redundancy. Thus multiple small units provide graceful degradation upon failure. I can replace a failed one easily or at worst adjust my priorities and power less.