You can't simply pop the boot on a motorcycle when you need to store luggage. Installing a flat rack to the back of your motorcycle makes carrying luggage too big for your saddlebags much easier. Building one is rather simple since the bulk of the structure is a sturdy, flat piece of metal. To help ensure that nothing falls off the rack while you're riding, a lip needs to be added around the edges. The shape of the rack is partially determined by the shape of your bike.
Measure the space behind your seat. The rack will extend from the back of the seat over the fender and out to the sides. Pay close attention when measuring the width of your seat since the luggage rack will be cut to fit around it.
Make a template of your planned luggage seat onto an old cardboard box. The luggage rack should be roughly rectangular in shape with an indent on one of the longer sides to accommodate the back of the seat. Cut out the template and check it against the back of your bike. Adjust the shape and size of it until you're happy with the result.
Trace the outline of the template onto a piece of sturdy sheet metal. Cut out the base of the luggage rack using sheet metal shears.
Cut out three additional strips of metal to use as upright lips along the edge of the luggage rack. The lips should stand approximately 2 inches tall and stretch along the entire back and both sides of the rack.
Fasten a minimum of three metal brackets to the bottom edge of each lip (corners and middle). Pre-drill holes for the brackets then secure them with nuts and bolts.
Secure the lips to the outer edges of the luggage rack. Place the lips with the brackets facing inward along the edge of the rack and mark the location of the bracket holes. Remove the lips and drill holes for the brackets. Attach the lips to the rack with nuts and bolts.
Place the rack onto the back of the bike directly behind the seat. Mark the location for the bolts that will attach the rack to the bike's back fender. You need at least four bolts set up in a square formation. The exact shape of the fender will help you decide the best possible location to ensure that the rack remains stable.
Remove the rack from the fender and drill out the bolt holes. Place the rack back on the fender and mark the location of the bolt holes onto the fender. Drill out the holes then fasten the luggage rack to the back fender.
You can adjust the height of the lips to better suit your needs.