BeOn Automotive SL, offers the 450 GP Kit, which consists of a kit of parts that allows you to modify a motocross / enduro motorbike to make it suitable for use in track. 
For a reasonable price, and these non-intrusive modifications, you can have a real racing motorcycle 450cc 4 strokes for use on race tracks and off-road, as the Kit 450 GP can be assembled or disassembled in a very short time. 
The kit comes complete, so it is not necessary to modify the original bike. The retail price of the kit is 4450 € (*). It also supplies separate parts for the kit. 
For further information, contact 
(*) The price does not include VAT or shipping costs.