Total loss of Electrical power

1981 KZ650-CSR. Scorpion AGM battery (08/2015). Ctek US 0.8 smart charger. Ninja 500 voltage regulator.

No electrical power. no lights. no headlight. no starter. nothing. fuses tested good (continuity).
Ignition switch off -->> Battery = 12.89 VDC.
Ignition switch on -->> voltage drops drastically to like 1 or 2 VDC.
With brown wire disconnected at the ignition switch & Ign switch on, the voltage drops to around 9 VDC.
Is the problem likely to be the battery? I was going to try to do a load test by rigging up the headlight to it or maybe by jumpering the starter solenoid, but I lost momentum yesterday after checking a bunch of other stuff. doh. .... Thanks in advance.

1981 KZ650-H1 wiring diagram -->> i.imgur.com/nxc8yZE.jpg -->> opens in new window. then click to enlarge. it's big.

Anything connected to the ignition switch, that can pull a *good* battery down to 2 volts, will blow the main fuse. So with that behavior, battery would be the first suspect. Did the bike run poorly at idle right before you shut it off the last time it ran?

Your load test sounds like a good idea. Then charge it and try again, to see if it is bad, or just discharged. If it can run the bike, you should be able to see if the charging system is working.

Two years on a Scorpion is not normal. My buddy, who also has multiple bikes, and I have been getting 5 to 7 years.

It looks like your AGM battery is shot.
Out of my expirence, i have shot three of them in one year.
Now all my bikes have LiFe-ion batterys. They pull so strong you can drive with the starter.
Have you cross check with an other battery befor you go deeper into unnessary search?

Thanks. It'll be a real drag if it's the battery as i recall reading good things about the ScorpionAGM.

It started like normal & was running fine. then I stopped at the bank drive through, shut off the engine, then tried to re-start. nothing. tried checking & swapping fuses. nope. After pushing the bike home, I checked the battery & it was showing 12.89 VDC.

ps: pushing a motorcycle 2.5+ miles in the August heat was not fun. good exercise, though.

If the battery will sustain 12.89, by itself, with no load, there is a chance you should have been able to bump-start it and ride it. Since we know the battery is not pulling it's own voltage down (through an internal short , etc), if you pulled the headlight fuse and tail light fuse, so that only the ignition had power, I would have expected it to start with a bump-start (or even a kicker if you have it).

No kick starter on the 81 650. I did try to bump start it out of the bank driveway, but that didn't work. probably didn't do it right. not enough speed, etc. In the past I have bump started a Ford Ranger, but never the KZ650.

You would have to make sure the lights and any other accessories were not connected in order to bump start. Pulling those fuses are probably the easiest way.

Thanks. At the time I was thinking the problem was probably something else like the ignition switch. and thought it couldn't be the battery as it's exactly 2 yrs old & well maintained, and I was expecting this AGM to last several more years.

Last night, I tried jumpering the starter. the solenoid clicks, but nothing else happens. the voltage drops significantly. So I'm pretty sure the problem is the battery. I should have suspected the battery first. wasted a lot of time & effort checking other stuff. doh.