I'm at the big boss in the sky.Is it all about timing,because I can't seem..

It can be about timing but when you taken it's armour off and hit it a few times then it starts to trick you by blowing fire away from you then turning to where you are going so you fly into it. So when it blows fire and pulls it's head back quickly go the other way and use the clawshot on the spot on it's back. Hammer it like mad but be careful and look out for the finish sign at the bottom or you are just wasting time.
Hope this helps.

Some of it is about timing, but it's mostly down to patterns because he likes to spit fire in a clockwise direction then change suddenly, my advice is to use Z targeting to get behind him (press Z again to change direction if he does) then use manual targeting to get onto his back.

It is pretty much all about timing. You just need to target the floating things (can't remember what they're called) and keep clawshotting them until you can see his back. Then you just stop targetting and manually aim for that big crystal.

Note: I own the NGC version of this game, not the Wii version, but I'm guessing the principle's the same.

No, it's all about persistence, just keep going around - eventually you'll get behind him, then lock on and slash away...