that's how my 49 cc is...no intake manifold.
the carb is bolted right to the cylinder with some long studs with nuts on the ends.
this carb is totally different than the standard nt carb, and it's a 13 mm.
this carb can be found on china made 4 quads, pit bikes and pocket bikes.
the carb itself works great but i think it's a tad too small. it's also a pita to get the carb off to re-jet, adjust the float, etc.
on the up side, this set up is excellent for 20" frames (which is what mine is) because the lack of an intake manifold, frees up room for clearance between the air filter and the seat post tube.