I used to repair those generators. No, I do not have any schematics. However Century Powermate built most of the store branded equipment. Therefore Snap-on, Sears, Montgomery-Wards, Coleman, Schauer, any of the automotive part store chains branded generators, welders, battery chargers, etc are all built by Century Powermate. The only differences are typically sheet metal and paint.
If you can find a schematic for a similar sized private label brand generator, it will probably be the same schematic.