I just set out to get wood for the winter. MS 290 ran great one month ago. I filled both tanks and fired it up. In the time it took to cut one five inch branch, the saw started running rough. It sounded like it was two stroking like when at full throttle with no resistance, but it kept getting worse. Finally the saw died. I could choke it and pull a few times then restart without a problem. Within about 30 seconds, it started the whole thing again. I thought maybe a bad fuel filter so I opened the fuel cap and was supersized to find that half of the fuel was gone. There is no evidence that gas was running out of the saw anywhere. Could it be in the crank case? Keep in mind that the saw only ran for a total of a few minutes.