'81 KZ550, stranded last night. no lights/no spark

Everything was okay, then I killed my battery trying to compression test. I borrowed a neighbors auto battery charger while my Battery Tender was in the mail. His was a 10 Amp automatic charger so I figured it might work. This is also before I knew about the < 10% amp-hour charge rate.

That battery went bad, nearly exploded. Whoops. Bought a new one, set it up correctly, charged overnight on the Battery Tender, I put it in, everything seems great.

This was yesterday. I rode around and it seemed like when I turned the engine off it would have trouble starting. Then it sat at a friend's house for 6 hours while I hung out. The battery was so drained at the end of that, the starter wouldn't turn, and the neutral light was barely on. I charged it there for an hour, it started, I left it to warm up in the driveway while I grabbed my helmet from inside. Come back out, it's dead with a dead battery again. Wtf?!

Charged it again, it started and I took off, hoping to make it home. I thought while it was idling maybe the RPMs weren't high enough to provide current to run the bike. I was suspecting a dud battery at this point.

Halfway home the lights went out, it started lagging, then backfired so hard I thought the cops would come. 3am, middle of the deserted city, dead bike.

I got a tow and after mishaps made it home at 6am.

Where do I start? What's going on? I have a multimeter.

It sounds like your charging system is not charging the battery. That means you run it dead when riding and everything crashes.

I figured that's the issue. How can I start diagnosing this? Work back from the alternator (or another part) or work from the battery on? Do I need a charged battery, or a running engine, to figure out what's going on?

Check your stator there might be a youtube vid on it for you bike Always charge a bike battery low volt slow or trickle charge never jump start your bike from a car or truck if the gas gets pushed it can blow your stator charging sytem quick charge can blow the stator as well. Good luck.

www.electrosport.com has a troubleshooting page, and also sells replacement stators(the wire windings), and maybe a rectifier/regulator for your bike.

Thank you both. I checked the output of the alternator and I get 12 VAC on each phase. That's definitely not right. I must have blown the stator with my overcharged battery?

I hope new ones arent expensive :pinch:

EDIT: $119 at Electrosport?? Oh man

Other websites to look at:
www.rmstator.com
www.customrewind.com
www.regulatorrectifier.com
www.accel-motorcycle.com/
www.tpe-usa.com/ (Tim Parrott Enterprises)

I took the stator off and inspected it, it looks fine. Nothing burned, rusted, or deteriorated.

I tested resistance across two of the three yellow output wires, repeating until I tested all three pairs, and got ~0.6 Ohm each. That's a little higher than my manual says (0.3-0.5 Ohm) but is it cause for concern? I also tested resistance from each of the yellow wires to the stator cover case, and there was no short.

What is the correct way to test alternator output? With the engine running and choked to 4,000 RPM I test for VAC from one of the three yellow output wires to ground, repeating until I've tested all three. The first time I did this, with a cold engine, I got ~12 VAC for each wire. Low. I repeated the test after reassembling the stator and am now getting ~36 VAC for each wire.

Multiplied by 2 that gives 72 VAC, which is correct for how much I understand the alternator should be putting out.

Am I measuring it correctly? Measured to ground am I supposed to see 70+ VAC? Or am I supposed to measure by putting both of the voltmeter probes into separate yellow wires? The manual I have says

3. On models with 3 yellow leads from the alternator: Start the engine and connect an AC
voltmeter (0-250 volts) to every pair of yellow leads in turn (there are 3 combinations). The meter should read about 75 volts AC. If it is much lower, the alternator is defective

you need to check beween the yellow wires, 1-2, 1-3, and 2-3. that would be the correct way. I am guessing the you will find 75vac then.

Tyler wrote: you need to check beween the yellow wires, 1-2, 1-3, and 2-3. that would be the correct way. I am guessing the you will find 75vac then.

Tyler has the procedure right, but with 3-phases, the measurement will be more like 50 to 60 Vac on each of the three possible pairs.
The older, single-phase stators will measure 75 Vac on the single pair. Some manuals have it wrong or don't mention the 3-phase version.

This link has additional info for the curious:
home.comcast.net/~loudgpz/GPZweb/GPZAltn...rnatorWaveforms.html

To ground, the volt reading is almost meaningless. But you should measure the ohms from each wire to ground. Each should be infinite.

blue_ltd wrote: I took the stator off and inspected it, it looks fine. Nothing burned, rusted, or deteriorated.

I tested resistance across two of the three yellow output wires, repeating until I tested all three pairs, and got ~0.6 Ohm each. That's a little higher than my manual says (0.3-0.5 Ohm) but is it cause for concern?

For any low Ohms reading (under a few Ohms) always measure the resistance with the lead tips shorted together and then subtract that value from the measured number to get the true value. A set of leads will usually have a few tenths of an Ohm resistance in them.

Thanks everyone. I found the issue. When I replaced the battery I nudged the cable from the RR to the battery and it disconnected. The cable end is destroyed, previous owner did a really bad job. I taped it back together for now but I definitely have to redo the ends to ensure this doesn't happen again.

Thanks everyone! I'm back on the road!