The two piece wheels found on most of the Honda 50's and 70's rust between the two halves next to the tube. This makes removing the tire difficult on older, more weathered, models. First, the bolts holding the halves of the wheel together need to be removed. Squirt some sort of penetrating liquid into any crack that you can find. This will help separate the bead of the tire from the rim. If the bead of the tire is not corroded to the rim, soaking is not necessary. If you soak the tire really well for a couple of hours, you will save some elbow grease later. Next, the tire needs to be pried away from the outside of the rim. Usually you can only gain a fraction of an inch at a time, working around the rim. After the rims are separated from the tire, it is usually necessary to have them sandblasted. The rust typically pits deep into the metal. Without getting down to clean "white" metal, you will be wasting your time. Remove any dings or dents at this point, before you paint. In some cases the wheel is rusted all the way through in a section where rain has been allowed to set for years. If it is rusted through all the way around the wheel, it is not worth going through the trouble of restoring. Weld the area up from the back side. If the front side of the rim needs it, make one pass on the inside of the rim. Be careful not to build up any more weld than needed, since you will be grinding this area next. After welding, grind back smooth. Clean the welded area with a wire brush, or if you have access to a sandblaster, go ahead and re-blast this area. If you have left grinding marks in the face of the wheel, a thin coat of body filler can fill them. I prime and paint the wheels next, and usually paint both the inside and the outside with acrylic enamel. This is pretty tough paint and will help keep rust from starting again. Hardner in the paint can make it more resistan to fuel, and other stuff. When reassembling the wheel, use permatex or some other type of silicone gasket material between the halves. Apply it liberally. When you bolt the halves back together, the silicone will squeeze out of the holes. Let it dry, and then you can peel it off, or run a knife around the holes to trim. This is the most important step, since it will prevent water from getting back inside the rim.