Ok I have an older kx250 (99 model) which looks and runs great. Most of my riding is at the track and when I race with guys I enter the D class and usually finish mid-pack.
I've ridden a YZ250F a few times and loved the power but the reliability and cost of reparing a blown motor scares me. If I were to buy a 4-stroke I would probabaly get a second hand RMZ450.
But pragmatism stops me from doing anything more than thinking about a new(er) bike. I could keep my kx and have the suspension revalved and maybe even replace all the plastic and powder coat the frame too.
I really want a 450F and have seen a few for $4000. I could swing it but I'm not sure I would be using my money wisely. Is it a waste to spend that much on a newer bike if all I'm doing is racing locally (in the D class)?