03-04 it was common for the axles to bend since they were not made strong enough. Same thing happened to the axle on my 04. Replace it with a after market one, I put a Durablue in mine.
2004 z400 Limited Edition, Cylinder Works BB Kit, LTR 450 Shocks, D.I.D Gold X Ring Chain, Pro Taper bars & grips, UNI Pro Flow, DuraBlue axle, Razr 2s front & back, Moose nerf bars, Moose Barkbusters, DG Pro V-lite front bumper, Pro Armour front skid w/PRM rear skid, 14T, Full Pro Circuit T-4 Exhaust, 25 pilot-3rd clip-146DJ Main, lid on w/ 1" vents, 850 feet elevation.
”You can watch things happen; You can make things happen; or you can wonder what the F happened”