There are severaI possible methods of repairing dents in frame tubes, depending on location, severity, wallet, and imagination. I have a Durifort Bertin that's a nice bike except for a shallow though large (1/4" deep x 1" circ) dent right on top of the toptube. Since the original paint is not damaged, I've been considering my options.
I've settled on trying the hydraulic method using a porta-power (a hand-operated hydraulic pump capable of 6,500 psi). The toptube is closed at the head-tube and has a small hole at the seat-tube. I'm going to rig a rubber plug with fittings and expander-bolt that will fit into seat-tube and allow attachment of the hydraulic line. I will fill the top-tube and fittings with hydraulic oil, attach pump and pump dent away. I believe the thin-wall tubing (at the dent) will be the first to pop. Pics before and after will be available next week (if successful). If unsuccessful and you don't hear from me again, this method is not advised.
Jack Romans
Sacramento, Calif