I am having a problem getting my mower started. Here is the problem. It is a pull start. I can't get it started with the pull start. But it will start when I remove the air cleaner and squirt some gas into the carb. Once started, I must run it for about 5 minutes in full speed and then lower the RPM's. It will then run forever. Once I shut it off and then try to pull start it, it won't start. Any idea's?