Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
Looks like a great idea .. I will have to try it. On the CB250RS I have just got, it came with a spare caliper but somebody had drilled and tapped the alloy housing to force the piston out and then fitted a short allen screw in order to seal up again (no sealing washer fitted either) . Ugly looking bodge though IMHO. I have drilled and tapped the piston before, when I knew the piston was knackered (as they usually are). I have never tried the grease gun method but piped up to a master cylinder and used the hydraulic pressure to remove the piston. This is what I did on the seized but unmolested CB250RS caliper that was fitted to the bike.
I used a method an old American bloke uses on his XS650 on YouTube, same principal but using a large nut and bolt wound out inside the piston, stick an open ended spanner over the bolt then a bar through the ring end to twist while pulling up gradually. Photos might help with this description 😀