I installed a Gentran swith in a house the other day and I checked out the generator (Generac 4000w), when I checked it I found the voltage from the hot leg to ground was 0 zip nada.... I tried to call Generac, and got a local sales rep who knew jack about it. I had a similar problem with a Honda generator (hot to ground was 65volts) and when I called them they said that was normal for that model.
Ok, so when these generator's are being used as a back up power source in a dwelling doesn't it become a seperatly derived system? And shouldn't the neutral be bonded to the ground in the generator?
I would appreciate anybodys input. Thanks in advance.

The generator only becomes a separately derived system if the transfer switch transfers the neutral (breaks the neutral). If that is the case then you must connect the neutral to the frame of the generator with the bonding strap. You will also need to install a grounding electrode. If the neutral is not transfered then the bonding strap must be removed and the neutral conductor is connected to the neutral terminal on the generator. The green grounding conductor from the house wiring is connected to the frame of the motor. In your case where you did not get a reading from the hot leg to ground may have been because the ground strap was not in place. I hope you got a reading from hotleg to neutral.