Assuming you normal house voltage is 120 volts, sounds like something is wired wrong. If you had the house (or part of it) running on generator and then took some voltage readings, you may have damaged some of the items in the house already.
typical voltages for residence is 110vac/ 127vac/ 200vac/ 220,240vac for single phase type
The four wire configuration has two 120V legs and a neutral and then a common ground. you will need to get a multimeter, set it to the "over 200 volts AC setting" then place your leads into the holes in the plug while the generator is running. this will let you find the two hot legs together they will equal 200Vac. to find the common ground power down the generator! set your meter to OHMS... make sure there is no power on when you use ohms! now take one lead and touch any exposed bare metal on the generator and the other lead into the plug until you read Zero ohms this is your common ground. the other will be neutral... if you take the plug apart, the two hot will be either red or black or both the neutral will be white and the common ground green. this is the quickest way to tell the legs now that you have identified the legs find a plug that works for your amp draw talk to a hardware store electrician for help on the plug... and hook it up p.s. The 220V appliance you are hooking up doesnt use the neutral (white) wire