Here is a pretty simple mod that Team Green did when they were racing the KX500 in the desert. I have one of their bikes and it has several mods that addressed the very few KX500 weak spots. Just to name a few, Team Green fixed the exhaust mount attachment to the frame from cracking, they welded up the radiators (and used shims to grab more air) including welding the air bleed, reinforced the frame and welded a u-shaped piece onto the frame to protect the water pump, and riveted a piece of stainless steel to the subframe to eliminate the chain wearing through it. Do a search and you can see one of my posts on some of these mods, and I attached a photo of the mod that addresses the subframe wear.
