Intermittent charging system failure ugh!!!

[kxpower?]

Sorry for the long post, TLDR: Bike leaves me stranded with dead battery, need to figure out how to diagnose.

So after finally getting this old beast bolted back together and lights, etc going well enough to be legal, took it out for a couple rides this weekend. Total of 26 miles just putting around town isn't too bad for a bike that's been in pieces most of the last 3 years. Man this thing is fun.

But I've had a failure 3 times, that I'm having trouble putting my finger on. One was at the garage after idling about 10 minutes to get warmed up, the other 2 times were while I was out riding. I'm just cruising along, then the engine suddenly loses power, pull the clutch in and it will idle but give it any gas an it just chokes up and dies. First time I lucked out and pushed it 100 yards back to the garage, and the battery showed TEN VOLTS! But it fired right back up when I jumped it off my car, and battery voltage came back to 13 or so, so the charging system had come back at that point.

Second time it failed out on a ride the same thing happened, it lost power and the battery didn't have enough juice to turn it over. Of course, being the ready-for-anything kind of guy I am, I pulled the jumper cables out of my backpack and got a jump from a guy who stopped to help. Fired right up, but this time when I disconnected the jumper cable it immediately died. So it wasn't back charging yet. The guy gave me a ride to the house so I could get my car; I went back later and jumped it off and rode it home, no problem.

So I think we can say with some certainty that the charging system is failing. I suspect it's going to be heat-related, since all three times it acted up after running a good while, and all three times it worked again after some time to cool off. But here's the problem, how do you ID which component is failing? My gut says the rectifier/regulator (and luckily I have 2 or 3 spares laying around), but when it intermittently fails I'm on the side of the road unable to restart and run the engine and chase it down with a meter.

I guess the good news is that it probably actually fails several minutes before the battery discharges to the point that it can't run the ignition, so I think next time I take it out I'll wire in a multimeter and put in in the map pocket of my tank bag and watch the voltage when I ride. When I see it drop off I'll swap out the rectifier and see it the voltage comes back up.

Anyone have any tricks for something like this? Any other components that are prone to overheating?

[alex.s]

proper charging is 14.7v.

could be the battery. could be the voltage regulator.

typically when you jump from a running car it blows the VRR.

[kxpower?]

Originally Posted by alex.s

proper charging is 14.7v.

could be the battery. could be the voltage regulator.

typically when you jump from a running car it blows the VRR.

Hmm, highest I remember seeing when running was about 13. Should I be seeing 14.7 at idle or does it need to be revving a little to make full voltage? I may stick a spare in there just to see if the voltage gets better with another vrr.

And I've been creeping around here long enough to know better than to jump off a running car. Had to tell the guy who jumped me off to turn off his engine

[alex.s]

i think its supposed to be at 3k at least when measuring. a screwed battery will draw extra but not keep it. a short or fried leg on the stator coil could also cause it. with it off you can check the resistance between each leg of the stator coil. they should all be the same (i think the ninja coils are around 300ohm... don't quote me... but as long as theres no short or open and they're close...)

[rgx107]

A good start would be to charge the battery with a motorcycle charger and make sure it's OK. You anyway need to do this if the battery has been down to 10 V, it goes bad very quickly if you keep it at that low charge level. I get a feeling though that the battery is shot and one cell is bad (resting voltage 10 V). Perhaps that overloads the charging circuit so it shuts off to prevent overheating.

[kxpower?]

Originally Posted by rgx107

A good start would be to charge the battery with a motorcycle charger and make sure it's OK. You anyway need to do this if the battery has been down to 10 V, it goes bad very quickly if you keep it at that low charge level. I get a feeling though that the battery is shot and one cell is bad (resting voltage 10 V). Perhaps that overloads the charging circuit so it shuts off to prevent overheating.

The battery seems to be OK, after charging up with a charger it starts and everything just fine, and there's not any problems except when the charging system goes down.

[kxpower?]

Originally Posted by alex.s

i think its supposed to be at 3k at least when measuring. a screwed battery will draw extra but not keep it. a short or fried leg on the stator coil could also cause it. with it off you can check the resistance between each leg of the stator coil. they should all be the same (i think the ninja coils are around 300ohm... don't quote me... but as long as theres no short or open and they're close...)

I hadn't considered that, I'll check the resistance when it's cold and jot down the numbers, when it fails I'll see if something changes.

Also, maybe a dub question, is the flywheel cover (that the stator is behind) supposed to be in the oil bath? I seem to remember the flywheel being dry on some bikes, but they might have been 2 strokes. Thinking if it's sitting in oil from a leaky seal and it's not supposed to it might cause some trouble.

[csmith12]

If it's truly intermittent, it's most likely the battery is going bad or a wire is not tight. Have the battery tested somewhere or do an in depth test yourself, loaded, unloaded and full charge.

Otherwise.... Check your wiring on the stator and rectifier. The stator can be ohm tested, the rectifier cannot. So checking the stator is the first step beyond the above simple checks. There is a high and low side to your rectifier. Assuming the wiring is fine, if you got no voltage coming out, either the stator is not producing or the low side of the rectifier is out. If your getting over the spec voltage the high side is out and your gunna smoke the battery. Either way, you're buying one or the other and sometimes... both.

Oh, the ninja doesn't require a certain rpm for the stator/rectifier to work as it should, but I do the voltage tests at idle (1300-1500) and at 3-5k rpms just to make sure the voltage doesn't spike at higher rpms (high side test).

Good luck and let us know if you find anything.

[csmith12]

Oh! stator should be dry, if not... you got a seal leak.

[kxpower?]

Originally Posted by csmith12

Oh! stator should be dry, if not... you got a seal leak.

Oh boy...

[jgcable]

Sounds like a bad cell in your battery. Just replace it.
Same thing happened to me several times over the years.