Yes that gas can make a difference in starting. So can clogged up passages in the carb, I always drain mine. Try this, drain the old gas and put new fuel in, remove the carb take it apart & clean it with a fine tooth comb, set the float height and reinstall. Remove the air filter element and clean & oil it but leave it off. Pull the decompression lever and kick it thru about 10 times. Turn the idle screw up a full turn, flip the choke on, slowly kick it to TDC then return the lever to the top and kick it thru. Do this 3 to 5 times if it doesn't fire do the 10 kicks to clear it and then try again. If you still have nothing replace the plug and repeat, if that doesn't do the trick check your valve clearances, adjust as necessary and repeat the starting proceedure. If that doesn't work I'll be amazed.