STOP!!!
No rattle guns!
(sorry scooter thats for old models)
Can you see the three bolts that form a triangle on the top. There is one next to the black pull starter handle, one is near the muffler and the other is near the carbie (black yucky cruddy thing).
Undo these and the top will come off with the starter. On this model there is no top crank bearing and when you remove this you can see inside the sump area.
Once you have it off give it a clean with a rag. Off to the mower man and he will fix it for you.
Get a new o'ring and replace the old one that fits around the top of the inside of the pull start, add a light wipe of oil on it and reassemble. While at the mower shop grab a new plug and air filter. When you get back take the fuel tank off and give it a clean with some fresh new fuel, refill and away she goes.
cheers
dazzler