Originally Posted by sojudave
You bike is already welded. That dude might not be to smart. I have tried to mig weld a bike frame, but I burned through it. I am not a good welder yet either. I took it to a guy I know and he smoothed out some of my mess with a mig, no problems. I'm sure it depends on the frame. If the metal sparks when you hit it with a grinder, then it is steel-ish. If it simply turns to dust, it's probably aluminum.
Or use a magnet, besides ferrous welds wont stick to alluminum Thats how I get broken steel studs out alluminum heads, I just put a nut over the broken stud and weld it on, weld only sticks to steel