I cleaned my fenders with the oxalic quite a few time and didn't work. Since I belive it's from the dye from my friend pants (english saddle pant), I guess it's can't be removed. So I decided to darken my saddle a bit with canola oil. It's came out better then I though but not as good as I was hoping for. Unless I dye it very dark I guess not much can be done.
Thank for the info, hopefully the next stain will not be as bad... none, will be better
Lesson learned : Stain from pant's dye and saddle, not a good mix !!!!!
I may add picture later, so poeple can see the after, just right now it's not possible.
Thanks & have a good day !