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Offline DrTearjerker

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puzzled by stator readings.
« on: 16 July, 2020, 08:16:29 PM »
hey guys, i changed my battery a while back because starting and re-starting after short drive in particular became an issue.
the battery of my MK1 cbf1000 was pretty old so it was due.

Now after a few times that i went on a drive the battery charge was low yet again.

I suspect the stator, but my readings throw me off.

First i would like to say i am not very good with the multimeter, its sorcery i tellz ya!  :165:

fully charged; 12.65V
ignition on: 12,15V
engine start: drops to between 10,50v -11V
engine runs: back to about 12,15V
revving up to 5000rpm : voltage goes up slightly to 12.35V (max)

tested the stator i get readings between 00.3 - 00.4 Ohm (the manual says between 0.1 and 1ohm)
the lowest selection on my meter is 200 ohm so it reads 00.3 -00.4 and that would be 0.3-0.4 Ohm.
when we deduct the 0.1 resistance from the leads that leaves 0.2-0.3 Ohm that would indicate it is fine. but i suspect it is tired and in need of replacement :027:

after that i tested the rectifier ,and seems fine.

So i think i will be replace the stator anyway, what do you guys think?



« Last Edit: 16 July, 2020, 08:17:30 PM by DrTearjerker »

Offline FLIZ

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Re: puzzled by stator readings.
« Reply #1 on: 16 July, 2020, 09:59:10 PM »
When revving up to 5000rpm you should be getting more like 13 to 14 volts. If you search the forum you will find plenty of advice to help with diagnosis of stator and rectifier.

Offline g5guzzi

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Re: puzzled by stator readings.
« Reply #2 on: 16 July, 2020, 10:00:26 PM »
Hi DrTearjerker
did you check each of the stator wires to earth? there should be
no circuit if there is any circuit  to earth its scrap.
the other test is to start the engine then test all 3 stator wires in pairs
to each other with the multi meter set for AC volts  when the engine is revved up
you should get in the region of 55 to 70  volts AC on any pair.

Malc

Offline DrTearjerker

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Re: puzzled by stator readings.
« Reply #3 on: 16 July, 2020, 10:21:47 PM »
*Originally Posted by g5guzzi [+]
Hi DrTearjerker
did you check each of the stator wires to earth? there should be
no circuit if there is any circuit  to earth its scrap.
the other test is to start the engine then test all 3 stator wires in pairs
to each other with the multi meter set for AC volts  when the engine is revved up
you should get in the region of 55 to 70  volts AC on any pair.

Malc


thank you for the tips.
as i come to think about it. i did do a ground test already (did so many tests i am not even sure) but i think all 3 pins beeped to ground but i somehow thought that was normal and as it should be? but now that you said it, its obvious to me its not.

i will do both tests tomorrow to be sure.
« Last Edit: 16 July, 2020, 10:34:12 PM by DrTearjerker »

Offline DrTearjerker

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Re: puzzled by stator readings.
« Reply #4 on: 16 July, 2020, 10:24:56 PM »
*Originally Posted by FLIZ [+]
When revving up to 5000rpm you should be getting more like 13 to 14 volts. If you search the forum you will find plenty of advice to help with diagnosis of stator and rectifier.

yes Fliz, that i did know.
I plowed thru all treads but couldnt find a clear answer to my specific issue.

Offline Art

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Re: puzzled by stator readings.
« Reply #5 on: 17 July, 2020, 05:52:21 AM »
*Originally Posted by DrTearjerker [+]
Ignition off battery voltage of 12.65v is good
Ignition on battery voltage of 12.15v is OK
Cranking engine battery voltage drops to 10.5v is good
Engine idling at 1,200 RPM battery voltage of 12.15v suspect an alternator or charging circuit fault
Engine running at 5,000 RPM battery voltage 12.35v suspect an alternator or charging circuit fault

tested the stator i get readings between 00.3 - 00.4 Ohm means the stator coil resistance is
the lowest selection on my meter is 200 ohm so it reads 00.3 -00.4 and that would be 0.3-0.4 Ohm yes
when we deduct the 0.1 resistance from the leads that leaves 0.2-0.3 Ohm that would indicate it is fine. yes yes

what do you guys think? You need to confirm if the low voltage readings are due to a stator fault or a charging circuit fault

If you have tested for and found continuity between any of the three yellow wires from the stator to ground you have already confirmed that the stator is faulty and no further testing is required. Replace the stator and then re-test the charging system output expecting around 13v across the battery terminals with the engine idling at 1,200 RPM and greater than 14v but less than 15.5v with the engine running at 2,500 through to 5,000 RPM.

Just in case you need to eliminate a charging circuit fault. With the ignition switched off check and note the battery voltage then back probe the Regulator Rectifier side of the RR connector red wire to green wire and the voltage reading should be the same as the battery voltage. With the engine idling at 1,200 RPM check the voltage drop from the RR connector red wire (back probe the connector on the RR side with the multimeter red lead) to the battery positive terminal, expect less than 0.2v. With the engine idling at 1,200 RPM check the voltage drop from the RR connector green wire (back probe the connector on the RR side with the multimeter red lead) to the battery negative terminal, expect less than 0.2v. If greater than 0.2v disconnect, clean and check all terminals, connections and fuses between the RR and the battery, fix the fault and re-test.


Top tip - Make a note of the voltage readings and keep for future reference, check the battery and test charging system output as each 4,000 mile service interval.
« Last Edit: 17 July, 2020, 06:18:18 AM by Art »

Offline iNCORRIGIBLE

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Re: puzzled by stator readings.
« Reply #6 on: 17 July, 2020, 08:56:51 AM »
DrTearjerker....I would say your meter skills are pretty good.Alternator is definitely TOAST!   Art's advice is sound & you may well also have a charging or other fault such as leakage of charge.Ed.
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Offline DrTearjerker

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Re: puzzled by stator readings.
« Reply #7 on: 17 July, 2020, 07:46:35 PM »
thank you all for the great advice, i will be sure to test for a charging circuit fault aswell.  :037:

Offline Art

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Re: puzzled by stator readings.
« Reply #8 on: 18 July, 2020, 11:33:18 AM »
When you have lower than expected voltages across the battery terminals with the engine running it is important to test further because the cause can be so many things other than the stator. You need to prove the stator is faulty or eliminate the other parts of the system that can cause low voltage. In this case you proved the stator was faulty by testing for and finding continuity between the stator coils and ground.

If you're getting battery voltages greater than 13v idling at 1,200 RPM and greater then 14v but less than 15.5v at 5,000 RPM then the charging system, wiring circuit, stator and regulator rectifier are fine and there is no real need to test the system any further. That said there is no harm in testing each part of the system if only for the practice, future reference or plain curiosity. The sequence to test is battery, circuit, stator and regulator rectifier. Fix any fault found and restart the testing from the battery.

For future reference and out of curiosity I fully tested my charging system after replacing a faulty stator and made the following notes in the vehicle service schedule record

8th June 2017, 31,180 miles
battery level of charge 12.5v
battery standby current drain 0.1mA
battery voltage cranking 10.8v
battery voltage idling at 1,200 RPM 13.8v
battery voltage at 2,500 RPM 14.2v
battery voltage at 5,00 RPM 14.2v
battery positive terminal voltage drop to regulator rectifier red output wire 0.11v
battery negative terminal voltage drop to regulator rectifier green ground wire 0.11v
stator output yellow wires 0.1Ω across all three pairings
stator output yellow wires no continuity to ground
stator output yellow wires 40 vAC across all three pairings at 5,000 RPM
regulator rectifier forward bias diodes (yellow to red) 0.12v
regulator rectifier forward bias diodes (green to yellow) 0.5v
regulator rectifier reverse bias diodes (yellow to green)  1.
regulator rectifier reverse bias diodes (red to yellow)  1.
« Last Edit: 18 July, 2020, 11:35:25 AM by Art »

Offline iNCORRIGIBLE

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Re: puzzled by stator readings.
« Reply #9 on: 18 July, 2020, 12:07:24 PM »
Masterful!  :020:
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