Another couple of other tests to consider are:

with a fully charged battery, measure the battery voltage while pressing the starter button for 30 seconds, with the run switch in the off position. The voltage should stay above 10 volts, the higher the better, and indicates the capacity of the battery.

also with the engine running the battery voltage should stay in the 13-14 volt range at 5000 rpm with all lights on, tests the capacity of the charging system to support the total electrical load of the bike and still charge the battery.

Le_Blur wrote:I was measuring the voltage in AC first time round. What do you mean across each phase? From each yellow wire to earth?

You noted that it was 12v across each phase...that is too low.

You need approx 45+ and it rises with revs.

Measure it on each of the yellow wires
1+2
2+3
1+3

If you are getting 12v AC then your genny is dead..

My GSXR genny does 70+ AC Volts....it is a beast..lol My reg rec could fry shit.

CMSMJ1 wrote: You noted that it was 12v across each phase...that is too low.

You need approx 45+ and it rises with revs.

Measure it on each of the yellow wires
1+2
2+3
1+3

If you are getting 12v AC then your genny is dead..

My GSXR genny does 70+ AC Volts....it is a beast..lol My reg rec could fry shit.

Any chance you could explain the whole procedure on how to do this check -safely- as in what point on the wires you check them and how to avoid getting electrocuted?
Thanks,
David

Please note that if you test the alternator with the rect/reg connected, as Le_Blur has done, you will not get 50 VAC. The rect/reg will stop the alternator output voltage getting above the battery voltage + a couple of volts ie 13-14 volts max. This is why the alternator needs to be disconnected from the rect/reg during testing.

Thanks, Magg. So my output might not be too low after all. Additionally, the AC voltages were taken with the positive test node on one wire and the negative to the terminal. I think I need to double check this one.

Easiest way - unplug the genny at the connector by your right knee - use the probes on each connector wire on the genny side.

Le_Blue, your problem will be disconnecting the alternator if you have hard wired it to the rect/reg. This is why I suggested the lights on load test. If you can get 13-14 volts at 5000 rpm with max electrical units operating at the same time it will tell you that the charging system is ok. If you can disconnect the rect/reg from the alternator then you should measure the voltages as CMSMJ1 indicated, yellow to yellow wires.

Thanks for your help guys. I might try both ways. I was gonna have the lowers off anyway to sort my exhaust gaskets amongst other things, and I need to check that other earth point, so I might as well do it all in one go.

Cheers,

Luke

Luke there is no earth wire for the alternator , it does not use one. Three yellow wires is all you have to worry about. Resistance and output voltage between the three yellow wires is what matters.