I was setting on my trike, outside a dealership. 3 riders pulled up and parked along side of me. They exited their bikes and were standing outside the entrance door. I happened to take notice to one of the riders bike's seats. In one spot of the seat. A pin hole size spot on their seat started to smoke. I called to one of the riders and said your seat is starting to smoke! he rushed over and sure enough. In one little spot it was starting to burn and melt! He immediately started taking his seat off, which ceased the smoke and the burn that was taking place. What had happened. Is that when they pulled up and the way they were parked. The sun was reflected from one mirror to another's mirror and then to his mirror and then to the seat. It acted just like when one uses the sun through a magnifying glass to pin point the intensity of the sun's ray. Luckily I was there to notice this. It would have been a bummer to come out to a bike fire! And never to know how it ignited.