Electrical /battery goes dead

1973 K2 ct70.just bought new battery but it wont stay charged.when running bike the light gets brighter(charging?).after riding for a while I can turn engine off and turn key to lights...headlight is bright...several days later the battery is about dead.any ideas?? Scott

I am not an electrical or CT70 expert, so hopefully someone else will post here too, but I would try connecting a voltmeter to the battery (+ to +, - to -) and noting the battery voltage with the bike turned off. Then start the bike up. If the voltage remains the same or drops, the battery is not being charged. If the voltage increases significantly as the rpm of the engine increases, your charging system is working. If the charging system is working correctly, I would look for a problem with the bike that is causing it to draw down the battery while it is stored. If the charging system isn't working, you then need to determine where the problem is.

If this is bad advice or someone else has a better idea, please correct me.

Seems like it is charging,light gets bright during and after riding but I'll check it out.Scott

On a CT70, without the bike running, the headlamp should not be on. It may just be the early and late models, but on my K0 and K1 and my 1991-1994's are like that.

If that's the case, then you have your wiring buggered somewhere and the lights are running off the battery and not the stator. With the key on and the bike not running, only your horn and taillamp should be lit up.

Please provide more information on wiring modifications you've done or the previous owner did..

On my K2,there is a 2 position key switch.position 1..bike/motor on no lights,position 2 bike/motor/lights on.Scott

Dan's right about the headlight being run directly from the alternator output. Still, even if your wiring has been modified at some point in its history, that alone shouldn't drain the battery if the lights are off. I've wired my bikes so that the headlights draw their power from the battery and haven't had any problems with battery rundown...even after sitting for weeks at a time.

First thing to do is disconnect the battery from the bike when you think it's fully charged. Then let it sit undisturbed for the same duration and see what happens. If the battery is down on power, then it's either not holding a charge, only surface charged or simply not completely charged, when you believed it to be. If, on the other hand, it remains fully charged, then you'll have determine what's drawing current while the key switch is in the off position.

A fully charged battery should indicate somewhere around 6.5Vor better. Below 6V indicates a discharged battery.

As far as I know there have been no wiring mods,I'll try pulling the battery and let it sit...it's brand new so I hope its good,thanks Scott

See if theres a voltage draw between the battery & + cable diconnected with the key off. Look for a wire short if there is