My lawn mower doesn't start?

my lawn mower is 21 "cut begger/mulcher,6.50HP engine,190cc,TD LLC--- run from gas & it has prime.14 days before when I was mowing my lawn & it was almost done suddenly some smoke was comming out form my lawn mower, but it was running. yesterday I changed oil and poured gas and tryed to run it,it started but few sec.later it stoped.I saw some gas/ oil driped from air cleaner filter. I tryed several times but it did not work. what should I do now ? why my lawn mower does not start ?Could someone help me please