What: Shares of natural gas engine technology expert Westport Innovations (NASDAQ:WPRT) cranked up more than 12% on Nov. 6, and for no obvious reason whatsoever -- at least on the surface. 

So what: Today was a relatively strange day for Westport's shares to trade up in such a big way. There wasn't any fundamental news material to the company's business or prospects. Oil prices were down slightly, and that's typically correlated with Westport's stock falling. There was pretty significant trading volume on the day, with the roughly 784,000 shares trading hands more than double the recent average. 

Now what: Westport's stock price has plummeted in recent years as the company has struggled to ignite growth, knocking its market cap below $300 million. That makes Westport's stock much more subject to big momentum swings. With Westport set to release third-quarter earnings after market close on Nov. 9, some of today's run-up is probably short-term traders looking to "get in" before the earnings release, counting on a "pop" if the company reports good news. 

In other words, there's no news beyond volatility that's at least partly due to the upcoming earnings release. Stay tuned for earnings coverage next week. For now, buckle in. It's probably going to be a bumpy week. 

Jason Hall owns shares of Westport Innovations. The Motley Fool recommends Westport Innovations. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.