I have a Billy Goat 33" FM3300 walk behind mower with a Briggs INTEK 13 HP engine. I just had it serviced a few weeks ago and it ran fine when I got it home, however, I wanted to clean the deck underneath so I turned it over on it's side (the side opposite the discharge chute). I worked on it for about an hour that evening and left it that way during the course of the next day. When I got home from work I found that most of the oil had leaked out through the top of the engine. Now the recoil won't go past 6 inches and it stops ... I don't know whether the engine has "locked up" or has "siezed up". I can't see how it could have siezed up because it wasn't running, the oil just leaked out. Any thoughts, ideas or comments ??