Of course its on the intake and its on basically every vehicle ive seen. What is its purpose and name?

 

One of Honda's true specialties is tuning an intake to make it quiet and flow great, that box is to stop reversion noise in the intake pipe. At one point they threw around numbers like 3 million in development on the intake box for the S2000. I used ot know a race team that ran them, they dynoed hundred of them looking for an edge, for all around performance the honda part always won.

 

If you want to impress your acquaintances, call that thing by it's real name:
Helmholtz resonator

https://en.wikipedia.org/wiki/Helmholtz_resonance

In the linked article, look about half-way down under APPLICATIONS

 

Yep, looks like a resonator box. They were pretty common on 2 stroke dirt bikes.

 

I would love it if the L15 was a two stroke,, K-power plus with half the weight..