One of my favorite parts of motorcycling is the smells. If you've never experienced the world at high speed without a bubble of metal and glass in the way, the smells are rather startling at first. They're so intense, and so fleeting.
Here's a wisp of woodsmoke. There's a pine forest. There's a skunk, in all its glory, oh god - but the next breath, it's gone, like it was never there. This air is so fresh. That's something burning. (Are my pants catching fire on the radiator? Nope, feet and legs are still in the non-smoking section.) Someone's doing laundry. There's a farm full of cow manure.
And on it goes. It's one more way in which biking is a more intense experience of the road than driving a car.