Hi Marcos
1. How do you know that it don´t have the ballast wire?
2. With the "sport" Lucas coil, the golden one, you don't need the balast. It starts and runs allways with 12V. Commonly they start with 12 and runs with 6V.
3. To stay on "the safe side" you can buy one balast from ebay or directly from Rimmer Bros in England.
At last but not the least. I live in Portugal, I'm portuguese and the techical secretary of Triumph Club de Portugal (www.triumphclub.pt).
Hope this helps