Hm. I can't remember XY much so I'm not sure when you get it. Still though, if you play your strengths you can win.
If your Talonflame could out speed the Magneton a solid x2 STAB fire type move could potentially one shot it.
You should have been through the Power Plant by the time you do Clemont, so if you have the TM for Flame Charge teach it to your Talonflame.