Cuts out when headlamp turned on!

[KEVINBACON]

Hi, bike starts fine but cuts out as soon as I turn on the lights,
When running only the brake light works and gets brighter the more revs I give it
I suspect the battery is on its last legs as well, the lights do come on without the bike running
But very dimly!?

[Mike40M]

What bike?

[KEVINBACON]

1970 starfire

[rhyatt]

You really need to establish voltages to start your diagnosis and understanding.
Using a meter  check battery voltage, nothing on.
Then check voltage when it's running.
If you unsure of the battery, then you must charge it first , prior to any checking of charging

[DANFINN]

Is your alternator working? I had to replace the whole unit on my C15 because the stator was a different size to the new style ones.