Managed to find some bulbs that should work -- checked the brake light and it does. Changed the rear signals but have yet to test them, since I have had those covers off.
That leaves me with the instrument lights and headlight to find and the front signals to change, all of which require fairly major disassembly to get to. It will be street-legal again as soon as I get the front directionals working, at which point I'll do some test-rides to make sure the rectifier/regulator doesn't get wonky at cruising speeds.
2 months ago