Sounds like a problem in the ignition switch. The switch has 3 positions. Off, On, Park...In park, only the tail light comes on. I am assuming when you say "Break Light" you mean the rear light in the lower brightness mode. Brake light is quite a bit brighter.
In the "On" position 12 volt power is supplied to the tail light and the ignition. There are 2 wires for that. the tail light is a brown wire, the other lights are brown and white, ignition is black.
Start at the back of the ignition switch. In off, 12V only on the red wire. On "on", Black and white, brown and brown/white should be powered. In Park, Brown only.
If power getting through, then check at kill switch....Black wire should have 12V, black/white should have 12V when the kill switch is "On". Then check for 12V at coil black/white....
If you are missing power after the ignition switch, it is likely to be a loose connection in the headlight bucket, or, under the tank....
Don't waste money buying parts until you have the problem identified....A voltmeter, if you don;t have one, is the first thing you need. Even a cheap one from Harbor Freight will work, and they often are free (I have 3 of them). A good one (I have 3 Very good ones too) is better for troubleshooting actual voltage levels as they are bit more accurate.
Do you have a schematic? The right one for your Year? Since you haven;t really siad the complete model and where your located, I don;t know what of the 7 or 8 different schematics might apply to your bike. In the US, the 74 and early 75 model are different then the late 75 and 76 models.....Without a schematic and a systematic approach, you often buy parts you didn't need to, as you have already learned.
