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Discussion Starter #1
Hello chaps!

I just rebuilt a CB500T in the UK and everything seemed to be working fine untill I decided to test the charging system.

I'm reading 11.5VDC at the battery with the key off. When I start it , it reads 11.7V and when I rev it , it goes to 11.9V . If I turn the lights on, it drops to 11.5 (This is a European model, therefore I can turn the lights off) Ok, so it's charging but just a little bit.

There are no burnt wires/contacts. There is no terminal corrosion and all plugs are as good as new.

I've tested the stator for AC output and only got good readings on 2 of the 3 testing connections. I cant find anything specific about testing these charging systems and my knowledge here is very scarce, therefore I beg for help.
 

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Sensei
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There ARE only two possible/reasonable readable positions originally.... Pink to white or pink to yellow.... you CAN jump the white and yellow together and read to the pink as well...IF you get 25 to 30 VAC across pink to any of the other possibles, the "alternator' is OK and doing its job (problem in rectifier, regulator, or battery itself...)
 

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Discussion Starter #4
I have now replaced the rectifier with one I thought was ok and I get the exact same readings. Also the readings are exactly the same ones if the rectifier is earthed or not to the frame. This is odd.

The battery is brand new and acts like it.

Is there any way to test these rectifiers? Can the regulator have any effect on this?

Thank you
 

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Sensei
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Disconnect the REGULATOR and carefully rev while checking DCV across battery terminals..... Rectifier MUST be grounded to complete the circuit, but the green wire is actually a redundant ground, so if it is connected, you ARE "earthed".......... :D

OHMmeter readings across any two rectifier wires should be low in one polarity, and switching red and black probe positions should show infinate in the other direction....
Lack of any reading = open diode.... relatively low readings in both directions = shorted diode..... Either condition = replace rectifier.........................
 

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Discussion Starter #6
Progress so far.


1- After checking AC voltage output on the stator(unplugged), readings say it's working properly.
2-Both rectifiers (bike's and spare) are giving good readings, meaning they're both working.
3-By disconnecting the regulator, absolutelly nothing happens , when it should jump up the DC reading at the battery.
4-Reading stator output pink and yellow plugged in, gives me 14VAC not increasing with revs.


I would also like to add that this is a absolutely stock bike with 15k miles. The wiring is very clean, uncorroded and has never been touched , cut, extended or fixed by anyone.

Thanks Steve.
 

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Discussion Starter #7
Ok, so I managed to draw a simplified diagram of the CB500T charging system.

From this:




Into this:


Although I still find hard to understand why the white/yellow wire goes all the way to the connectors box, just to change to yellow?

Some where in that drawing is the answer to my problem.
 

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I'm watching this topic with a great deal of interest as I have exactly the same problem with my 450.
Except I have much greater readings 45v AC from my alternator.
Somebody please help..
 

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Discussion Starter #9
Bike-Mart said:
I'm watching this topic with a great deal of interest as I have exactly the same problem with my 450.
Except I have much greater readings 45v AC from my alternator.
Somebody please help..

Have you tried measuring the output voltage with the stator plugged in? Pink to yellow in the rectifier plug?

What revs do you get those 45V?
 

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I get that reading at about 2000 revs.
As yet not tried measuring output at rectifier plug as I'm sure my problem arises from where the wires go to headlamp in loom.
By wiring my alternator directly into another rectifier and then to a remote battery I.m getting 14.0v at battery.
As soon as I utilise bike loom all useable voltage seems to disapear 11.9v even with new recitifer and disconnected regulator.
 

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Discussion Starter #11
That's well thought! I'll test the stator, rectifier and regulator using another loom to another battery.
Because you cant find parts for these bikes anymore (unlike the 450) I had to buy 2 more for scavenging purposes.

I'll try that tomorrow mate! Cheers
 

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Sensei
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500T charging system and parts are identical and interchangable with ANY 5-speed 450 (DOHC type)...

THIS has been posted at least four times....:
 

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Discussion Starter #13
So far I've checked:

Rewiring the charging system to another battery with rectifier without regulator and it gives me 15vDC idling.

Using an external OEM loom - same low voltage

disconnecting headlight -same low voltage

disconnecting clocks- same low voltage

disconnecting tail light - same low voltage

disconnecting regulator - slightly higher voltage (0.5V+)

disconnecting ignition barrel - same low voltage

disconnecting dash - same low voltage

disconnecting hand controls - same low voltage


The bike runs and starts first time, every time on the button or kick, every bulb, indicator,
EVERYTHING either mechanical or electrical in this bike works as it should....but the charging system.

Any opinions as odd as they might seem?
 

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You are now in exactly same boat as me.
I intend spending all day tomorrow on it, will keep you posted.
 

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Sensei
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So far I've checked:

Rewiring the charging system to another battery with rectifier without regulator and it gives me 15vDC idling.

Sounds like a bad regulator to me.......
 

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Discussion Starter #16
Being the kind kind of guy that just cant let go without finishing the jigsaw puzzle, I've come to the following conclusions during my "sleep"...

The wiring on my bike is different from the Haynes diagram for the CB500T and yes, it took me all this time to realise that because I'm a slow thinker :lol:

The Haynes diagram is for the US model with light permanently on, therefore the white wire from the stator is permanently connected to the yellow.

I found the Haynes diagram for a cb450 5 speed European is very similar to mine except for a few wire colours.

I still have a few tests to do , but so far I can only see two options. Either the stator is giving me acceptable readings and looses performance under load

or there's something draining too much power in the system. That "something" can only be the coils, once I've bypassed or unplugged everything else in the wiring system.

Now the question: Can the coils drain too much power? I dont think they can. They still are the original OEM ones and I'm not too sure about being properly grounded due to the slight corrosion.
I forgot to mention that I rebuilt the engine and put everything back together to run it for a bit and solve all other problems (like this one) there might be,
therefore I havent powdercoated the frame yet.
As I see it poorly grounded coils who lead into misfiring and this engine runs very smooth.

Anyway, I appreciate all inputs and ramblings.

Cheers!
 

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The points ground the coils...If they weren't grounding, the bike wouldn't run....
 

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I have spent all day checking mine through, right down to adding earth wires to all and everything.
I have come to the conclusion (as you state) that the alternator is giving readable output untill it is put on load, then it fails. I have a couple of other stators to try and with a bit of luck they will have wiring colours that match one of the diagrams I have. My stator has one white(ish)/yellow(ish) wire, one pink(ish)/yellow(ish) wire and a greenish/grey wire.
 

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Discussion Starter #19
Bike-Mart said:
I have spent all day checking mine through, right down to adding earth wires to all and everything.
I have come to the conclusion (as you state) that the alternator is giving readable output untill it is put on load, then it fails. I have a couple of other stators to try and with a bit of luck they will have wiring colours that match one of the diagrams I have. My stator has one white(ish)/yellow(ish) wire, one pink(ish)/yellow(ish) wire and a greenish/grey wire.
I hink we need to get together, drink a few bottles of wine and then... get to work on it.

Maybe then we can get to a conclusion :p
 

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Eureeka !!!!!
Turned out to be one of the wires in the stator was leaking to earth, stuck a bit of epoxy over it and everythings OK. Don't think it will last very long so am on the lookout for a good one.
 
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