Alternator failed for third time

**MikeL** · 28th July 2010, 09:17

Coming back from a short pootle on my CB-1 on Sunday the bike conked out. Battery dead. I'm immediately overcome with a sense of deja vu. Fortunately (thank you, CB-1) it chose to die about 1 km from home, all on the flat or downhill. Got home, charged up the battery, bike started instantly, got out the multimeter, knowing full well what I'd discover: no charge from the alternator. So what? Pretty common scenario. But wait, there's a catch: this is the third time!
In 80,000 km the alternator's been rebuilt twice already - once at about 30k and again at about 60k.
Question: am I unreasonable to expect an alternator to last more than 20-30k?
Does anyone else have a similar story?

**Paul in NZ** · 28th July 2010, 12:07

Of course it should last longer - makes you wonder whats going wrong and if you are treating the sympton and not the fault causing it?

**F5 Dave** · 28th July 2010, 12:52

I've had multiple failures from rewound stator.
Turns out my local guy was rubbish.
JH rewinds from then on have been reliable.

**karmobRob** · 28th July 2010, 14:34

Were the previous rewinds or new stators?

**F5 Dave** · 28th July 2010, 17:32

Originally Posted by MikeL

. . .
In 80,000 km the alternator's been rebuilt twice already - once at about 30k and again at about 60k.
. . .

Answer in 1st post.

**Motu** · 28th July 2010, 17:50

I went down the same road with a Honda - 3 stators.It was the regulator...even though it was showing 14.5 volts charge,it was dumping everything else it could put out and overloading the alt.I didn't catch it the 2nd time because the CDI coils failed,which were part of the stator.

**Flip** · 28th July 2010, 21:16

Originally Posted by F5 Dave

I've had multiple failures from rewound stator.
Turns out my local guy was rubbish.
JH rewinds from then on have been reliable.

Who is JH?

**Kickaha** · 29th July 2010, 06:26

J.Halsey Rewinds, Auckland
0-9-534 4161

Top service when I used him after F5 Daves recommendation, just over a week turnaround time including freight

**MikeL** · 29th July 2010, 08:00

Originally Posted by karmobRob

Were the previous rewinds or new stators?

Rewinds. Don't know who did them. 1st was through Mt Eden M/cycles, second through Red Baron.
Anyway, I'm getting a new reg/rec. Considering what I've read about the unreliability of these units I'm surprised it hasn't failed completely before this.

**vifferman** · 29th July 2010, 08:55

It's actually very easy to diagnose a stator fault versus a failed R/R. You need a multimeter to do this. Unplug the R/R, and measure the resistance (multimeter on "Ohms" setting) between each of the three yellow (or sometimes white) wires coming from the engine casing (i.e., from the stator) into the R/R. All readings should be between 0.5 to 2.0 ohms. If they're not, there's a broken wire in a stator coil.
Next, check the reading between each lead and the engine casing or some other ground/earth point. All should be zero (no conductivity). If any of them aren't zero, then that stator coil is shorted out.
Lastly, measure (using the AC voltage setting on the multimeter) the output from each yellow (or white wire) with the engine running at 5k rpm - it should be more than 50V AC, and all three wires should read about the same.

If all these tests pass, you can check the R/R by measuring the voltage at the battery. Firstly, check the battery is OK. The voltage should be over 12V (healthy is around 12.7-12.8ish, but if you've been running the bike with the battery not charging, it will be lower.
Start the bike; at idle the battery voltage should be over 13V (typically 13.5ish). As you rev the bike, the voltage should rise to around 14.7 and shouldn't get higher than this above 5k rpm. If the voltage doesn't rise, or if it goes over 14.8, the R/R is toast.

**Paul in NZ** · 29th July 2010, 09:30

If you put a new R/R on - my recommendation would be to run an extra earth cable from its mounting point back to where the battery ground is located as well as another one from there to the engine cases.

**Motu** · 29th July 2010, 12:42

And put it in the airflow if it isn't already.That's what killed a lot of regs,they were tucked away out of sight and overheated.

**Juzz976** · 29th July 2010, 13:34

Originally Posted by vifferman

Next, check the reading between each lead and the engine casing or some other ground/earth point. All should be zero (no conductivity). If any of them aren't zero, then that stator coil is shorted out..

If the reading was zero this would mean a short to ground, I'd be looking for Out of Scale or anything above say 200kΩ would be a good reading. Or beep continuity test beep = fail
At least the way I understand insulation resistance testing.

**vifferman** · 29th July 2010, 15:43

Originally Posted by Juzz976

If the reading was zero this would mean a short to ground, I'd be looking for Out of Scale or anything above say 200kΩ would be a good reading. Or beep continuity test beep = fail
At least the way I understand insulation resistance testing.

Oops - my bad. Typed that in too much of a hurry.

Yes, you're quite right; not zero ohms, but "to infinity and beyond!" (or a close approximation thereof...)