Is 16 too old to start dirt biking?

I asked myself that same question when I was 13. Then I bought a bike a bit small for me but that was easy to handle. It was a CRF 80F. Within a couple months of learning and riding i was doing wheelies and building large jumps and tabletops. Now I have a CRF 150R. To answer your general question, if you are a fast learner, you are never too late or too old to start dirt biking. Also, you should get a bike that is kind of small for you or maybe even rent a dirt bike to learn first. then when you are ready and you have learned, you could get a really big bike and not have any problems riding it. For you, I suggest either a CRF 230 or a TTR 230. these trail bikes are a lot easier to learn and to ride then my CRF 150R race bike. try to stay away from 2 strokes and race bikes until you learned how to ride. I suggest you buy used if you do not want to rent because you wont get your money back. Good Luck!