Most portable generators sold in the U.S. have the neutral bonded to the frame. They are built and intended to be used as a portable power source and MUST be connected to a ground rod for safety. The 2014 NEC Article 445.20 REQUIRES that all cord and plug connected portable generators 15Kw and smaller have GFCI protection. This will require the neutral be bonded to the frame. The CPSC (Consumer Products Safety Commission) also has a similar requirement regarding neutral to frame bonding. In Michigan and in many other states the NEC is adopted as a state statute. Removal of a legally required safety device (Neutral-Frame bond) is not a smart idea IMO. Most generator manufacturers will also void the warranty when the neutral-frame bond is removed. The best option for using portable generators connected to building wiring systems is to install them as a "Separately Derived" system using a 3-pole transfer switch that switches the neutral. This will REQUIRE the installation of a separate ground rod for the generator. It MUST BE connected to that ground rod prior to each use. Note: See 2014 NEC Article 702.7 (C) and 702.11(A) & (B). This leaves the Neutral-Frame bond and the required GFCI protection in place and the generator remains safe for use as a cord and plug connected portable.