just got back from overseas, military duty, and my sd-50 wont stay running was running fine when i left, ran all gas out of carb and everything, got back, new gas and all, it will start and run for about 30 secs. and then cut off, wait about 1 min. try it again, will start and run again for about the same amount of time, the it quits again, any help out there, thanks in advance.