My drz 400s seems to have locked up on me. It won't start or even turn over. I can roll it in neutral but when in gear it is locked up solid. top end is fine [ already took it apart and its fine ] . Any ideas ? thanks.

Sounds like your camchain could of possibly jumped a tooth. Or maybe the lower cam chain sprocket is damaged. Just guessing at this point because it could be almost anything in the lower end.

How far apart have you had it; plug out and valve cover off, or the entire head? I'd say pull the clutch side cover too as you'll have access to a lot of the things that could seize, including the valve/cam train. If you haven't gotten as far as getting the plug out, try that to make sure it isn't hydraulic locked.

Thanks for the replies. Taken the head down as i  thought it was in the top end. Head, cylinder and piston are fine. Looks like im gonna have to dig into the bottom end now.