Rule #1 Never assume anything!

Rule #2 Go over the basics.
- Is the muffler tight?
- Is the Back preassure line attached and free of holes?
- Are all of the lines attached and run properly?
- Are the lines free of holes and securely attached to the fuel tank and nipples?
- Is the Fuel tank stopper tightened down?
- Has the tank been pressure tested?
- Is the Clunk in place with no bends?
- Is the tank mounted properly (even with or slightly abouve the carburator)?
- How long is the fuel line from the Tank to the Engine? Anything over 6" and a pump may be required?

Once you can confirm all of the above - then you can look at the engine for leaks etc.