Question.....should only one gas tank valve be open at a time? When I picked up my machine both were open. I took it in for repair cause the oil light was going on at idle and it was backfiring badly when shut down and running way too rich. It came back running fine, but only one gas tank valve is open now. Did having both valves open at the same time cause it to run too rich? Obviously it would make sense to have only one open at a time to avoid running out of fuel, but I did'nt even know there was a shutoff valve on it till I read about it in these forums. For winter storage should I shut them both off and run the gas out of the carb after adding stabilizer?