Purchased a new Exmark 21 last week. Great machine except for one problem. Having a hard time starting it first thing in the morning. I have tried shutting off the fuel at night, leaving the fuel on at the end of the day and also shutting the fuel off then run the fuel line dry. This engine does not have a remote throttle. I have an older Exmark that is equipped with the same type engine with a remote throttle. I can start this mower on the second pull. Any suggestions as to cause of problem.