Small Engines (Lawn Mowers, etc.): Carb pouring gas out the top, mtd yard machine, sure what kind

Question
I have a 2001 mtd yard machine with an 18 b&s engine. The problem; while turning the engine over, gas pours out the top of the carburetor and of course will not crank. It did the same thing last summer so I installed a rebuild kit. It ran fine the rest of the year but now its doing the same thing. It's so much gas that it soaks the air filter. Gas continues to pour out the top even when not trying to crank it. I have to clamp the fuel line off to make the gas stop running out. Any help is greatly appreciated. :0)

Answer
It sounds like you may have a venting problem.  loosen your gas cap and see if this makes a difference?  

If it doesnt, then you need to do a carb rebuild and check for a heavy float, and set your float height.  I am not sure what kind of engine you have as 18hp is pretty vague.  Please send me model type and code number of engine