This is going to sound silly, but i have to ask.
are you sure the gas valve is fully open? plenty of gas in the tank?
does your carb. have a secondary fuel shut off by where the fuel line goes in? is it open?
are you running a fuel filter? is it clogged up?
it's possible that a tiny peice of dirt got into the carb and could be clogging up the main jet. your float could also be out of whack, or cocked sideways in the fuel bowl. this would cause the needle & seat to be closed all the time and it would not allow any gas to flow into the carb. the needle & seat could also be stuck closed.
it could also be a bad spark plug, or a bad magneto...it's hard to say. the first thing you have to do is figure out if this is a fuel delivery problem, or an ignition problem.
pull the spark plug out and check to make sure it has spark (assuming that you know how to do that).
if it has spark, check for fuel a fuel problem. if it has spark, go get some starting fluid and spray a TINY shot into the carb throat with the air filter removes, and the throttle wide open. then try to start the engine. if it fires or attempts to fire, then you have a fuel delivery issue. there are a lot of things that can cause the problem you have, so you will have to do some troubleshooting on your own to determine exactly what the problem is.
oil coming out from where the exhaust pipe hooks to the engine is normal if the gasket is getting ready to go. the gaskets are cheaply made for these engines and they don't last long. get yourself an aluminum exhaust gasket from sick bike parts and put it on. it will seal better and last a lot longer than the fiber ones. put a small amount of high temp silicone on each side of the aluminum gasket before you install it.
it's nothing serious, just a leaky exhaust gasket.
