Can anyone suggest repair? It appears to be a riveted/press fit connection. Would some sort of adhesive do?
By your description, I gather you are referring to the pedal shaft (not the pedal), probably from an older Drive. You may be able to save it by
1. cleaning everything thoroughly
2. epoxying it back in place for temporary stability
3. Pinning it, as Hobie started doing more recently (as seen here):
Hobie now pins from the top, but I think the side might work out better for you.
The flipper masts have also decided to fall out now as well.
Your older "set screw" (also now known as "V-1) masts have fallen out because they have worked loose (either set screw backing out or widened mast hole or both) and you haven't been inspecting them very regularly before they fell out -- tsk tsk.
The newer threaded masts do not do this and are much better (you have to purchase the corresponding threaded sprockets also however).
The proper Scottish fix is to re-use the assembly rather than waste good money on a new set-up. Your best one time fix is as follows:
1. disassemble and clean set screws, masts and sprocket holes
2. file off the center ridge in the mast notch (for the reason shown here -- if you have that style) for full insertion of the set screw:
3. using a quality grade marine epoxy (Loctite Marine Epoxy for example), generously glue the mast AND seated set screw in place, insuring the mast flat notch is fully facing the screw and the screw is fully inserted (it will appear recessed into the sprocket). No need to over-tighten -- snug is good. (tip -- mark the notched side of the mast since you won't be able to see it. Slightly rotate the mast back and forth as you tighten the set screw to insure best seating).
Keep an eye on it. It should last quite awhile. When the mast finally begins to wallow, it's time to order the new style threaded masts, sprockets (and Turbofins if you're going to convert) Do this all at once so you don't have to waste money on a second set of masts later. It will come with Loctite Blue, which is the proper product to lock the masts in place.