Just my 2 cents worth, but now that I know you have a saw… remove the rear wheel and fender, then cut along next to the frame towards the bolt. It looks to be aluminium, so once you get to the bolt, you could take a flat blade screw driver and “lever” it apart. Good luck Edited to add: if strength is an issue, you can hammer a wedge “flat blade screw driver” into the cut made by the saw. Again, good luck