I've streightened a few motorbike forks in my pipe bender, always verify the metal has no stress raisers, marks or creases etc. Stretch marks blah blah. Basically if in doubt get a pro to verify but provided it's a slight bend and the tube remains un marked and round in cross section then it can be done carefully in a normal 10 ton pipe bender, using a bit of cloth on contact points to save the chrome from any marking. I checked the results by rolling the fork on a sheet of glass. I've found the scrap fork tubes are a great source of thick wall pipe for my various mini dumpers and other engineering projects. I've genrally found the headstock stem and frame wind up bent about the same time as the forks hit that point where I decide they are scrap, though I'd always check the frame is in line if I find bent forks.