Is it hard to maintain a 2006 crf450x. Do you have to remove many things just to work on the top end.?

Answer 1

The only top end work you'll need to do, is adjust the valves.
4 stroke engines rarely need piston and ring work.
To adjust the valves, just remove the fuel tank and the cylinder head cover - 3 bolts - simple.

Answer 2

guardrailjim is correct, other than valve adjustment you shouldn't have to touch the motor on the 450X. Just make sure you check the oil everytime you ride the bike. The 450X is a killer bike!!