So you have a blaster frame that needs touching up, and a motor that needs a wiring harness? Or you buy a blaster that needs a top end. I never heard of a 500 ex, but I would say get a wiring harness and continue with your project. Once it's done (If it's done right) that you will know it's good to go. You never know what you are buying. I blew the crank out of my KX20 the second time I rode it!