I bought my sister a Raleigh Sprite (which I'm guessing is 73 or later - Huret shift parts, italic decals, North Roads bars, Raleigh Sports adjustable levers and calipers, mattress saddle) that came with a dynohub front wheel. The rim is badly rusted and is missing 2 spokes, so I threw a pair of no-name steel wheels on there for the time being. I'd like to build this dynohub into a 700c wheel and perhaps use it for randonneuring, r at least, for fair distance riding and commuting, but don't want to go to the expense and time of building a new wheel with a hub that doesn't work. The magnets still pull (quite a bit), but is there a way to test it before building the hub, or do you need to have it spinning at "road speed" hooked to a light? How do you guys test these things before building the wheel?

Hook a voltmeter up to the wires, give the hub a spin with your fingers, and if it's not dead, it ought to show some varying voltage as it goes around. That wouldn't guarantee it was working right, but if it doesn't show any result at all, it sure means something isn't right.

They were fairly low power and heavy, so I'm not sure I would bother building it for actually doing all-nighters. It should put out some power even at low speed.

I think there are enough of them around that you can safely build the wheel and replace the dyno part if need be. The trick is not to separate the rotor and stator of the dyno.