Bit of a mystery here. I was mowing the lawn, going at my usual speed. Suddenly, the mower's speed slowed down to a crawl. It didn't give any indication of something wrong (that I recall). It still worked and I was able to finish, but everything was moving slowly. I took a long look under it, and couldn't find the source of the problem. All of the belts were in place, as were pulleys, etc. The engine is brand new, and has only been used for one season. The gas line is clean and it has plenty of fresh oil. Now, a couple of things that my have a part in this drama. The previous week, I had to retighten the large black pulley (V-Pulley?) that is located under the seat. It had come loose, and the belt had slipped off (I've done this surgery before as well as belt replacements). Worked fine afterwards, until the current problem. As I was crossing the yard, I came across a large hex bolt (pictured), approximately 2" in length. I have NO idea where it came from (or if it is even a part of the mower). There didn't seem to be any missing bolts underneath when I checked. Mower is a Troy Pony model 13WN77KS011. Any ideas?