could be an air leak?? could be many things... something with the EZ start... hopefully its not the piston/con rod...
someone mentioned to me, when mine wasnt starting, that you need Air, Fuel, and Fire... if you dont have 1 of those, you wont start... so check fuel lines, air filter, and try getting a cheap glow ignitor (thats what i did, and that was my problem)... Either way you go, good luck, and don't give up on it!!
If ya do, I'm open to donations on any sort of Revo!!
Fly it on my way!! LoL... good luck man!