Bad battery or bad rectifier/regulator?

[number9]

I have a strange issue that I'm not sure is related to the R/R. While trying to diagnose an intermittent temperature issue, I'd left the bike idling outside my garage for about 25-30 minutes. All of a sudden, the bike stalled. When I tried to restart it, I noticed that the dashboard clock had reset to 1am. When I tried to crank the motor, there wasn't enough juice to do so.

I store the bike inside during winters, and I typically have a Battery Tender hooked up to it. The battery is a Yuasa, but I'm not sure how old it is. It may well be original to the bike.

The funny thing is that, after the idling issue, I put the battery on a Tender. And today when I went to start it up, it started fine.

With my multimeter, this is what I could see:

Ignition off: ~12.3V
Ignition on: ~11.6V
Motor running: ~14.5V

Could this be an R/R issue, or is it likely to be something else? Charging issues are common on these bikes, so I just installed a VFRness in an effort to shore things up. With the ignition off, the battery (fully charged) voltage was about 12.5V. With the bike running and idling, the battery was about 14.3V.

However...

Once I brought the bike up to about 5000rpm, the voltage dropped to about 12.3V. Letting it go down to idle again, the voltage dropped further to 11.8V and kept dropping.

Do I have a bad battery or bad R/R?

[Jim]

Doesn't sound like a rectifier.
I thought they were around 12v at idle and 13v-14v at 5k RPM, but i could be wrong.

Are your connections to the battery solid and no exposed wires? How about that stator?

[number9]

Doesn't sound like a rectifier.
I thought they were around 12v at idle and 13v-14v at 5k RPM, but i could be wrong.

Are your connections to the battery solid and no exposed wires? How about that stator?

Engine cranks fine and starts so connections are good enough for that load. Wires look good, nothing exposed or shorting.

I know what the stator is but don't know how to test it...

[Jim]

I think you disconnect the stator from the battery and test the pins with your voltmeter.

I had battery, rectifier, and stator issues last March.

I remembered following the service manual on testing the rectifier and stator.

[Paul_E_D]

Sounds like a stator issue. My Triumph was the same when I got it. I actually replaced the R/R under recall and it didn't change, so I did the stator. Perfect since. I used an aftermarket Rick's stator. less than half of a stock replacement.

[cdovego]

2 stators in 10 years on my '05 CBR - bad stators and r/r those era. What year is yours?

[number9]

2 stators in 10 years on my '05 CBR - bad stators and r/r those era. What year is yours?

Mine is an '00 so built in '99. R/R is a SH579C-12, which is the OEM unit and supposed to be much better than the shit they put on 4th-gen VFRs.

[nhbubba]

I think you disconnect the stator from the battery and test the pins with your voltmeter.

If it is shot, another vote for Ricks. They are in Southern NH and did well by me.

[stoinkythepig]

I suspect heat may be causing the faulty stator to have an open coil. Has nothing to do with RPM (especially since the voltage stayed low when you let it go back to idle). Measure the resistance of the coils hot and cold.

[number9]

I suspect heat may be causing the faulty stator to have an open coil. Has nothing to do with RPM (especially since the voltage stayed low when you let it go back to idle). Measure the resistance of the coils hot and cold.

Thanks, I'll give that a try when I get home. I have the factory service manual too which I presume has proper resistance values to measure against.

I'll try the other suggestions in the thread as well.

How common is it for stators to go bad?

[Paul_E_D]

Pretty common on certain bikes.

[number9]

Pretty common on certain bikes.

Obviously the environments are different in terms of heat and vibration, but I've never had one go bad on a car. Alternator bearings, sure, but never the winding itself..

[nhbubba]

(Most) Motorcycles don't use automotive style alternators. They use a far simpler, lighter, not as robust stator + R/R system.
When you test the stator for resistance I believe you are mostly checking to see if it has an open circuit (infinite resistance) because the wire winding has burned. In my case the resistance of the coil checked out, but once I started the bike it became obvious that one of the windings wasn't putting out the required voltage. Once I pulled the cover I found out why:

[nhbubba]

Many (most?) of the R/Rs used in bikes are shunt type. As I understand it, these shunt any unused power right back into the coil. This means that if the electrical system of the bike is not loaded, the coils are sinking a fair amount of power. In my case I think the oil level got just a little bit low. This meant the coil was not fully bathed in oil. Combine the two and it meant for one hot stator. One of the coils melted, burned the insulation, and was no longer able to producing the voltage required. Thus I was discharging the battery at most engine speeds.

This kind of stator failure is quite common.

From here on out my daily rider/touring machine will have a voltage indicator on it. Signal Dynamics makes a really slick monitor that is just a single LED. Keeping tabs on the voltage at various RPMs is helpful to know the health of the charging system. In my case I only lost one coil and was still not entirely running off the battery. If I hadn't known the voltage was dropping, I'd have likely been stranded eventually. It also gives me an opportunity to do things to cut power usage like accessories, pull one or both of the headlight bulbs, etc. Give me an opportunity to limp the bike home.

I installed a voltage indicator on the VFR as well. Worthwhile insurance, me thinks.

[ZX-12R]

Many (most?) of the R/Rs used in bikes are shunt type. As I understand it, these shunt any unused power right back into the coil. This means that if the electrical system of the bike is not loaded, the coils are sinking a fair amount of power.

It's a little different than that. The generator on most bikes is a permanent magnet type that spins magnets around the outside of a stator. This type of generator produces a specific amount of power for any given RPM. To operate properly, the generator must always supply more power than the electrical system consumes so that the battery stays charged. The difference in power between what's produced by the generator and consumed by the electrics on the bike is handled in a couple of different ways. Lots, if not most, of the regulator setups (especially the inexpensive ones) will dissipate the excess power as heat on the DC side of the regulator. The less common but better approach is a regulator that can shunt the AC power from any combination of the stator windings to ground prior to it passing through the rectifier diodes. This takes a large portion of the thermal stress off of the more sensitive DC regulation components.

[Paul_E_D]

Translation: THey burn the fuck up!

[number9]

Either I'm really confused or my alternator is hosed. Or both.

With the R/R stator connector (3 yellow wires in a plug) disconnected, I saw less than 2.0V AC between each of the three terminals when idling at operating temperature. I haven't tested that at 5000rpm yet.

Here are the results of the rest of the FSM tests:

• 16-5 measured battery voltage: 12.3V DC (ignition off, cold) PASS
• 16-6 charging voltage inspection: 8.7-10.8V DC (engine running, operating temperature, 5000rpm) FAIL (FSM says <15V, but presumably means >12V<15V)
• 16-7 current leakage inspection: 0 mA (ignition off) PASS
• 16-7 alternator inspection: <0.3 Ω (ignition off) PASS
• 16-7 alternator inspection: no continuity to ground (ignition off) PASS
• 16-8 regulator/rectifier inspection: battery charging voltage between red/white and ground PASS
• 16-8 regulator/rectifier inspection: charging coil line open circuit FAIL (FSM says 0.1-1.0Ω)
• 16-8 regulator/rectifier inspection: ground line continuity to ground PASS

What do y'all think? What's really confusing me is that, engine running and cold, the battery will show good voltage at idle. Here is a table of values:

• Idle @ cold: 14.3V
• Idle @ 140°F: 13.3V
• Idle @ 160°F: 13.4-14.0V
• Idle @ 170°F: 13.9-14.3V
• Idle @ 174°F with high beam: 13.7-14.2V
• 5k RPM @ 177°F with high beam: 8.7-10.8V (this is the test from 16-6)

It looks like it is really breaking down under heat and/or RPM.

[ZX-12R]

What exactly is a charging coil line in the context of your VFR? I'm only used to seeing charging coils on small dirt bikes with very limited electronics. The VFR has a full sized stator.

Unless the clarification of what a charging coil line is leads me down a different path, your most likely culprit is the regulator has crapped out. A less likely cause would be a bad electrical connection somewhere in the system but this has the upside of not costing anything to check.

[number9]

What exactly is a charging coil line in the context of your VFR? I'm only used to seeing charging coils on small dirt bikes with very limited electronics. The VFR has a full sized stator.

The manual shows this test as a connector in the charging harness (red/white wire) and the battery ground. When I do this I can see the battery voltage, which is what the manual says.

Unless the clarification of what a charging coil line is leads me down a different path, your most likely culprit is the regulator has crapped out. A less likely cause would be a bad electrical connection somewhere in the system but this has the upside of not costing anything to check.

Right now I think the problem is the stator or some other part of the alternator assembly. If I'm only getting 2V AC out of the generator, then I might as well not even have an R/R.

[nhbubba]

You're only getting 2VAC out of the stator? All three legs? That sounds like your stator is toast. Isn't there a test to test raw stator output both at idle and at RPM? (See video above.)

On the SV/DL you pull the side cover and can inspect the stator. Sounds like that may be your next step. If it looks charred... probably your answer.

[ZX-12R]

Right now I think the problem is the stator or some other part of the alternator assembly. If I'm only getting 2V AC out of the generator, then I might as well not even have an R/R.

The 2VAC you are seeing at idle doesn't necessarily mean anything since that really needs to be measured at a higher RPM. You also said that your stator passed the resistance check however unless you have a higher-end meter, measurements of less than half an Ohm are usually fairly inaccurate. Connect your two probes together and see if you get a lower resistance value than the measurement of the stator.

My reasoning that it's likely your R/R is the fact that when your bike is idling, it has a high enough voltage to be charging but drops when RPMs go up. That is a scenario that a bad R/R can cause.

Measuring your stator voltage at a high RPM will be a lot more telling.

[nhbubba]

My stator passed the resistance check but failed the voltage test.

Although I now think Bill is right. I think bad stator would mean less than 14VDC across the whole rev-range.

[number9]

The 2VAC you are seeing at idle doesn't necessarily mean anything since that really needs to be measured at a higher RPM. You also said that your stator passed the resistance check however unless you have a higher-end meter, measurements of less than half an Ohm are usually fairly inaccurate. Connect your two probes together and see if you get a lower resistance value than the measurement of the stator.

I think it's below half an ohm when I measure the resistance of the DMM itself, but I'll double-check.

Measuring your stator voltage at a high RPM will be a lot more telling.

Will do!

My stator passed the resistance check but failed the voltage test.

Although I now think Bill is right. I think bad stator would mean less than 14VDC across the whole rev-range.

Can anyone recommend an auto electrician that's good with motorcycles? I'm not sure how much time I can spend troubleshooting this thing...

[Degsy]

I got to the "idled the bike for 25 minutes outside" and that was as far as I got. Fyi, Don't do that.

[Degsy]

Check voltage across legs of stator at about 5000rom. You'll be looking for 60VAC or so.

I'm confused. You're not draining battery, bike starts fine. Your only issue is a 0.1vdc drop at 5000 rpm? I'd say operating within design perameters, captain.

Or did I miss something?