Battery drain with key on

[owlneck]

Hi,
I have a 67 cb77.
I I just changed the front tire and started the bike turned the lights and a minute later it died. Could have died because it idles a bit rough too.
I checked the battery key off at 11.3. Then I check key on and it dropped to 7 and dropped quickly down to 3 and falling. I pulled out the key and It jumped back to 8.5 and slowly returned to 11.3 after a few minutes . The bike is fairly new to me. It was working fine with the lights on before . I had tested the rectifier and it was working ok . Sorry , that's all I can think of. I'm going to have a mechanic look at it soon but if anyone could recommend any basic causes. I don't have time for extensive electrical work at the moment. Sorry I don't have more to go on. I just wanna know if it's a short or a bad battery.
Thanks.

[kirbb9]

Very possibly a bad battery. Give it a good charge and then test it.
The battery should have 14.5 or so volts and 14 when running @ 3k.

Brady

[cadman]

Most likely battery - A full charged battery should show about 12.7VDC. If you apply a load - headlight - ignition - and it drops quickly - 10 minutes - then the battery is bad.

[kirbb9]

You're right cadman. I meant to say about 12.5 volts and 14 at 3k rpm.

Brady

[owlneck]

I charged the battery over night . Everything is fine now. holds a charge at around 12.5 volts
I guess I won't let the battery get that low again. thanks for your help.