hi im almost 15,a natraul athlete(i pick things up fast). im 145lbs 5'10'' and ride 4wheelers, snowmobile, and rode a pw 50 and an xr 85 last summer. im lookin to buy a bike pref under 1500$ and i was lookin at a yz, sx or kx 125 2 stroke but now im thinkin about a 250f cuz thats what my friends ride i want a mx bike because i will ride a lot of track and may consider racing but probly not i will also ride a lot of trails fields and hills. my big problem is i dont wanna put a lot of money into it i wanna get on one and ride and occasionly buy new parts. i have heard on 4 strokes u have to change the oil alot?