The generator of an engine-driven welding machine is comprised of front and rear housings that attach directly to each other. The generator stator maybe secured solely to one or the other housing with preloaded screws. Alternately, one or more preload elements may be interposed between the stator and one of the front or rear generator housings. Thermal stresses are thereby avoided between the stator and the generator housings, despite the housings being made of aluminum and the stator being made of steel. The rear generator housing has an end wall that is mountable to different selected internal combustion engines by means of teardrop shaped clearance holes and machineable bosses. Slots for cooling air in the rear generator housing have sides with tangential components. Air leaves a fan in the generator with tangential components that are matched by the rear generator housing slots. The fan incorporates both fan blades and a baffle having a close clearance with an annular wall of the rear generator housing. Side ducts in the rear generator housing allow cooling air to flow around the front generator housing and into the rear generator housing before being expelled out the rear generator housing slots.