Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What's happening: Natural gas engine technology expert Westport Innovations' (NASDAQ:WPRT) stock is down big today -- 14% at last count around 1:10 p.m. EDT. Earlier in the trading day it was down as much as 18%. 

Why it's happening: Westport reported earnings for its fourth quarter and full year 2014 after the market closed on March 9, and was actually up strongly during trading hours before earnings. 

The company reported a bigger loss than Wall Street analysts were expecting, which is at least partly behind today's big sell-off, but even after today's beating the stock is still up almost 50% from its low in mid-January:

WPRT Chart

WPRT data by YCharts.

The big-picture reality for Westport shareholders right now: This stock is likely to be very volatile, as a lot of questions remain about the company's future and its ability to move from cash-burning technology developer to profitable manufacturer. 

Looking for more coverage from Westport's earnings? Go here for my full take.

Jason Hall owns shares of and options for Westport Innovations. The Motley Fool recommends and owns shares of 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.