Lucas dynamos are often a source of trouble. But we have most parts to fix them again. Armatures, fieldcoils, brushes and bearings. When ordering armatures,please measure the length and have a good look at the drive end. When you replace all the 50year old parts and wiring and fit an electronic regulator/cut out switch (don't mess with those mechanical nightmares, you're not going to win) and use a fresh battery, it will be reliable for years to come, even at 12Volts. But the capacity remains limited. Try to cut down on power consumption by using LEDs.