danielson603: If you had tried that jump on a ttr-230 you would probably be suffering from a lot more than just an ankle sprain. The TTR bikes do not have the suspension for a MX track.
3rd infantry 101: The frequent top end rebuilds are not limited to 2 strokes, they are a high performance engine requirement. A four stroke MX bike requires them just like the 2 stroke MX bikes. Rebuilding a four stroke is a lot more work than a two stroke.
I noticed in your profile that a) you are 16, and b) your intention is to jump. This tells me that a TTR bike would be a terrible choice for you.
This thread should get moved to the "what bike do I get" forum, you will get better help there. Fill out the "sticky" at the top of the forum so that we know more about you. Bsaed on what I know now I would say that a ten year old 125cc two stroke would be a good bike for you.
Rod