Not sure about the VM16 carbs. I have noticed before that they cost more for some reason???
My friend Jamie (small engine mechanic) says that the VM18 is a 4 stroke carb. I'm not positive on it. I mean, my pinto got 64mph out of a VM18 and idled fine...
But, I've recently discovered the VM20 and oooooooohhh it's the cat's ass.
One of it's main uses is on Banshees which are 2 strokes.
Let me tell you the VM20 absolutely rips! Super duper easy to change the main jet too. No removal of the float bowl. Just pop out the main jet thingy with a 10mm wrench and change the jet in like 20 seconds.
Here's the VM20...
Here's a side by side pic of a VM18 and a VM20...
Good luck! Mikunis are the shit!