Just read this funny article about "6 Things Nobody Tells You About Owning a Motorcycle" and sadly it's funny and so true at the same time. I'm sure everyone has done a long day's ride fully covered in ATGATT only to feel all stinky at the end of the day due to heat, rain, bugs or whatever was sent your way as you rode down the road. I think this part pretty much summarizes that feeling:
But hey, sometimes you ride in the sun, and that's great! The open road, the warm summer air, and the heat ... oh God, the heat. A great deal of bikes, like mine, are air cooled. No radiator. So they're only really cooling down while you're in motion. When you're stopped (say, at one of those lights that doesn't recognize your existence) they're just radiating that heat upward, which happens to be right where your genitals are trapped. Aside from sterility and ball-burns, this also creates a nice pool of junk sweat. But don't worry: It will eventually evaporate into the rest of your clothing and skin, leaving you smelling like the floor of a teenager's bedroom for the rest of the day.
Read more: 6 Things Nobody Tells You About Owning a Motorcycle