Charging issue?

[W0LF6ANG]

Now that i have my ‘69 CT90 running fairly well i kept having an issue where it would die as soon as i would turn on the headlight.
Got a new rectifier and bike seems to stay on after i turn on the headlight but now i noticed that the horn doesn't seem to go off while headlight is on, but goes off when headlight is off.
I want to test the battery and would like to know what voltage numbers should i be seeing at idle, rev and possibly also while headlight is on while i try troubleshooting.

Is there something else besides the rectifier i need to look into replacing or testing to make sure it is working well?

Thanks in advance.

 

[ancientdad]

I'd look at the battery first to be sure it's okay. The small 6v batteries those bikes use don't have much capacity to support many things while these small, low-charging output engines are idling. The headlight is enough to cause loss of spark if the battery is weak, and at idle with a below-average condition battery it's easy to understand why the horn won't work when the headlight is on.

If the battery won't hold at least 6.3v after fully charged and resting for at least a half hour, it needs to be replaced.

 

[W0LF6ANG]

I'd look at the battery first to be sure it's okay. The small 6v batteries those bikes use don't have much capacity to support many things while these small, low-charging output engines are idling. The headlight is enough to cause loss of spark if the battery is weak, and at idle with a below-average condition battery it's easy to understand why the horn won't work when the headlight is on.

If the battery won't hold at least 6.3v after fully charged and resting for at least a half hour, it needs to be replaced.

The battery on it is a fairly new motobatt agm batter model mbt6n4

But i will check on that once i get home from work.

Thank you.

 

[W0LF6ANG]

I'd look at the battery first to be sure it's okay. The small 6v batteries those bikes use don't have much capacity to support many things while these small, low-charging output engines are idling. The headlight is enough to cause loss of spark if the battery is weak, and at idle with a below-average condition battery it's easy to understand why the horn won't work when the headlight is on.

If the battery won't hold at least 6.3v after fully charged and resting for at least a half hour, it needs to be replaced.

looks like the battery is holding a charge well. Stayed at 6.3 volts.

 

[ballbearian]

Clean every single one of your ground connections. CT90's are known for poor grounds. I'd run an extra ground from the rectifier to the battery negative terminal.

You can blow your sealed beam headlamp and other bulbs by riding at speed with a dead or low battery.