1050 gas gauge issue

I have run into the first issue with my two week old ST. The gas gauge does not read correctly. On the first tank of gas the gauge went from half full to one bar in less than 5 miles. I was a bit concerned, but decided to fill up and see if things would get better. Today I left my house with four bars shows and when I got to work there where two bars and the llow fuel light was on. When I left work the gauge showed over half a tank. I rode for about 25 miles and the gauge never dropped below half full and the low fuel light never came on. I stopped for gas and was able to put in 5.11 gallons so I was basically running on fumes. Any ideas what might be causing this problem?

Kevin