Apparently you haven't seen the inside of that engine...those carbs do not feed directly into the cylinders. That's a piston-valved engine. There are basically three ways to valve the airflow on a two stroke. The simplest and most common--especially with your weed wacker and MX bikes--is reed valves. The crankcase vacuum pulls thin flexible valves (reeds) open to allow the air in, and when the vacuum goes away, the reeds close. The little model Cox engines use these. Another way (which I believe was ruled out in MX racing because of its "unfair advantage" in the 70's) is the rotary valve. Basically at the end of the crank is a rotary valve that opens and closes to time the air coming in with the vacuum in the chamber. This is the most common system with RC airplane engines.

The third way, and the method used on the engine you see here, is I think called piston porting. The skirt of the piston acts as the valve. When the piston is down, the port to the carb is closed--the intake does NOT go directly into the cylinder. (You can tell by how far away the spark plug is from the top of the intake track.) When the piston is up (and there's vacuum in the crankcase), the piston skirt clears the port to the crank, and air/fuel goes in. These are cheap, because there are fewer parts than the other two methods. Sometimes an engine can look like this type, but in fact have reeds, and not the piston valve timing--they use the air velocity of the crank to help open and close the reeds.

I am not aware of any 2-stroke that has the carb intake going directly to the cylinder. You really need to get a book (or a half dozen) and read up on 2-stroke design if you want to build one. The $100 you spend on good books will save you many hours of frustration and failure trying to reinvent the wheel. There is an excellent article series in the strictly IC magazine. You really should invest before you start making chips.