So I am getting my step son a four wheeler for christmas and I am thinking about getting me another dirt bike to ride with him (I used to race them when I was younger). I am for sure getting a 4 stroke this time but I have a few concerns about them.

1) I have heard that the rebuilds on these are crazy high, like 1000+ to do the top end alone. Anyone have experience with this? I don't know if these guys are MX racers that are just beating on their bikes like crazy, but I wouldn't think that the 4 strokes would need a rebuild that often....but I have read differently. Also, they say the 250 (which is what I would want) require them much sooner than the 450. Any thoughts?

2) I would really like to get back on a MX bike, but how good is that going to be in the trails? Are they geared too high for the trails? I have read that they get hot more quickly as well. What do you think? I will be doing a bit of both but I have also thought about hitting some GNCC races if I get back to my old level of riding.