We are timeless, bound as one, we cannot be silenced, as our song lingers on.
To unlock full Hayabusa armour which includes the Helmet, shoulders and torso you must collect all 12 campaign skulls which should appear in the campaign options menu.
To access this go onto the campaign lobby and press 'X' and if it displays 8 Gold Skulls Iron, Black Eye, Tough Luck, Catch, Fog, Famine, Thunderstorm, Tilt and Mythic. As well as the 4 Silver Skulls Blind, Cowbell, Grunt Birthday Party and IWHBYD, you should have full Hayabusa.
I have never heard of this glitching up but of course the Katana does, although it is not Hayabusa it is often confused with it - the Katana requires any 49 achievements and 1000G.
Here's a video from Machinima to help you with the skull locations if needed: http://www.youtube.com/watch?v=pRQ-bOwMgco