So I go riding and shut the bike off. It makes a sound between a hum and squeal. Like a valve almost closing... Highly doubt it's anything serious but thought i would ask.

 

Real quiet humming? Gas tank vent probably

 

Did you or the previous owner remove the pair valve? It's a common mod (clean air mod) that increases crank vacuum. That humm is air sucking back into the crank to equalize with outside pressure. (it's normal after the mod)

 

I noticed that too after I did my clean air mod. I guess I never paid attention before.