Numerous options are available when making your own number plate for your dirt bike. Depending on your needs, and whether you want a temporary or permanent option, the materials will vary, but the main procedure will remain the same. Here you'll learn about a more permanent solution using plastic. Cardboard can be substituted for a temporary solution.
Using a tape measure, take approximate dimensions of the space available for your number plate.
With your utility scissors, cut out a square of cardboard the size of the dimensions you measured (for example, 12"x10") and place it over the space where you want to mount your number plate.
Trace out the shape you want for the number plate on the cardboard. Then trim the cardboard into the proper shape with the scissors. Trim until the desired shape is attained.
Punch two holes in each corner of the cardboard, at the mounting points, which will likely be the upper fork tubes or cross member below the triple clamp. Feed some garbage bag tie wraps through the punched holes to mount the cardboard on the mounting points. Make sure the cardboard stencil fits the way you want the final plate to fit. When you are done, the wire will loop through the two holes like a stitch and be secured around the fork tubes.
Remove the cardboard stencil, place it on the plastic, and trace the shape onto the plastic with the marking pen. Cut the plastic along the line to reproduce the shape of your stencil. Depending on the thickness of the plastic you choose, it may be necessary to score the plastic along the traced line with a utility knife in order to cut it.
Drill two holes at each corner of the plastic shape, in the places you marked out from the cardboard stencil.
Use the zip ties to secure each corner of the plastic to the available mounting point.
Use electrical tape to create your numbers of choice, and you now have a homemade number plate.
There are an infinite number of options with regard to the final materials and type of plastic. You can use flexible plastic cutting boards, "for sale" signs, old garbage cans, or mud flaps. Be creative.
Scissors and knives are sharp. Pay attention and be safe!