Mashermoto's Big Charging System Adventure

[Mashermoto]

Here is the patient. Just about every modification known on this form, but the modifications pertinent to the problem I'm having is: 1978 SE model, 277 rephase, PamCo ignition, Crane 8-3001 single fire 3 ohm coils, ElectroSport regulator/rectifier, stock alternator with new brushes and new aftermarket rotor.

I'm having trouble with the charging system. It has fried one regulator/rectifier and two rotors. I sent Jim the original rotor today to have rewound.

This is the original rotor. The epoxy has bubbled and darkened from heat. It reads about 1.5 ohms ring to ring and no short to ground.

This is the aftermarket replacement. It reads zero ohms because one of the lead wires broke off. Can't tell if it was from heat or vibration that caused it to fail. Either case, it only had about 500 miles on it.

Just so you know I do understand electronics and have a fairly good grasp on how the XS charging system functions. But sometimes I know just enough to be dangerous , so I read through Jim's charging system post and performed all the tests. The rectifier tests good. The regulator is allowing voltage to pass to the brushes (more on this later), so I believe it is good. I also wired up an automotive regulator and got voltage to the brushes also. The stator checks out good. So other than the rotor, all the main charging system components seem to be okay.

But here is where I need help. Jim's post suggested I should be getting battery voltage, or close to, at the positive brush with the key turned on. I don't. I am seeing about 1.5v or more drop. That could be the reason I'm burning up rotors because the lower voltage on the brown load wire going to the regulator could be tricking the regulator to send more voltage to the battery than needed, and therefore over working the rotor.

Following Jim's advice, I checked the red wire voltage from the battery to the ignition switch and it was good. Little or no voltage drop. However, the brown load wire voltage at the ignition switch showed the 1.5v drop. This is a fairly new ignition switch but I took it apart anyway to inspect it. No problem in the ignition switch. Well, cutting to the chase I found it is my ignition coils that are causing the voltage drop on the brown load wire. If I pull the fuse to the coil or turn the kill switch to off, I get close to battery voltage at the positive alternator brush.

So here are the big questions. Is that normal? Should ignition coils cause a 1.5v drop on the brown wire load circuit? In order to check voltage at the alternator brush should I cut off the coils first? Is it okay that the regulator can't tell the battery voltage is 1.5v higher than what is powering the regulator through the brown load wire?

These are things that just make me go Hmmmmm

 

[Jim]

So here are the big questions. Is that normal? Should ignition coils cause a 1.5v drop on the brown wire load circuit? In order to check voltage at the alternator brush should I cut off the coils first? Is it okay that the regulator can't tell the battery voltage is 1.5v higher than what is powering the regulator through the brown load wire?

Yes, the coils can cause a voltage drop on the brown feed circuit. How much? Depends... pri winding resistance... one or two coils.... to be honest, I've never measured the drop from the coils. Just shootin' from the hip, I'd say 1.5v is normal-ish.

I think there's a general misunderstanding about voltage drops. First, voltage drops are measured across something. Across the ignition switch for instance... or even across a connector or splice.
You said above "However, the brown load wire voltage at the ignition switch showed the 1.5v drop." So, that's saying you turned the key on, measured voltage at the switch connector's red wire (power in), then measured the brown wire (power out) at the switch and it was reading 1.5v lower than the red.

Is that how you checked it? Helps to be on the same page here. If you didn't check at the switch... say you checked at the battery red, and brown at the fuse block for instance, you put too many variables in play. Wire resistance, factory splices, connectors... the cause of the voltage drop could be in one of those as well as the switch itself.

 

[Jim]

I think there's a general misunderstanding about voltage drops.

Forgot to ramble on a bit more...

Another form of voltage drop comes from loads in the system. For instance, you turn the key on, which energizes the coils, causing the battery voltage to drop about a volt or so. This is a normal voltage drop. The coil is drawing power from the battery without the help of a charging system, so the battery voltage will drop slightly as it's discharging.

 

[arcticXS]

Forgot to ramble on a bit more...

Another form of voltage drop comes from loads in the system. For instance, you turn the key on, which energizes the coils, causing the battery voltage to drop about a volt or so. This is a normal voltage drop. The coil is drawing power from the battery without the help of a charging system, so the battery voltage will drop slightly as it's discharging.

The observed "voltage drop" across battery terminals when a load is applied (i.e something like headlight or ignition is turned on) is actually due to the battery's internal resistance. This resistance is larger in a small battery than in a larger one.
With a heavy gauge short across terminals, the voltage across terminals is zero.

 

[Jan_P]

Trying to think out loud
The frying of rectifiers and rotors Guessing the system is demanding output from the alternator to long and to high

As up here in north on 80 ies Suzukis starting in spring with low battery assuming the bike would charge up
Problem was the rectifier design was not such that it was able withstand any prolonged time Fried the regulator and then the alternator that was a PMA type I believe

So here the voltage drop 1.5 V might not be to high I dont know but can it be that there are some partial ground somewhere
the machine starts the regulator notices the system Voltage typically what is going to the battery ( across )
If that tends to be low the regulator rises the upside on the alternator trying to adjust up .But if there are this partial ground
or something uses to much fex Extra Headlights It is working the alternator at longer times at higher levels

Perhaps measure what goes through each fuse at power on -- se if something looks high
perhaps Smaller fuses in for test

The smaller fuses has the advantage that if it is a problem that come and goes the measurement wont show it cold but the smaller fuse catches it
when driving ..A voltmeter on the machine is a good thing to have.

Are the electrical specs for the coils suitable for the bike and pamco ?

 

[Jim]

The observed "voltage drop" across battery terminals when a load is applied (i.e something like headlight or ignition is turned on) is actually due to the battery's internal resistance. This resistance is larger in a small battery than in a larger one.
With a heavy gauge short across terminals, the voltage across terminals is zero.

Was trying to keep it in simple terms.

 

[Mashermoto]

Yes, the coils can cause a voltage drop on the brown feed circuit. How much? Depends... pri winding resistance... one or two coils.... to be honest, I've never measured the drop from the coils. Just shootin' from the hip, I'd say 1.5v is normal-ish.

I think there's a general misunderstanding about voltage drops. First, voltage drops are measured across something. Across the ignition switch for instance... or even across a connector or splice.
You said above "However, the brown load wire voltage at the ignition switch showed the 1.5v drop." So, that's saying you turned the key on, measured voltage at the switch connector's red wire (power in), then measured the brown wire (power out) at the switch and it was reading 1.5v lower than the red.

Is that how you checked it? Helps to be on the same page here. If you didn't check at the switch... say you checked at the battery red, and brown at the fuse block for instance, you put too many variables in play. Wire resistance, factory splices, connectors... the cause of the voltage drop could be in one of those as well as the switch itself.

You are correct. I measured red power in at the switch to ground, then brown power out at the switch to ground. The difference in readings was approximately 1.5v.

 

[Mashermoto]

Forgot to ramble on a bit more...

Another form of voltage drop comes from loads in the system. For instance, you turn the key on, which energizes the coils, causing the battery voltage to drop about a volt or so. This is a normal voltage drop. The coil is drawing power from the battery without the help of a charging system, so the battery voltage will drop slightly as it's discharging.

This type of voltage drop is what I thought was going on. I didn't really consider the coils at first. As I traced through the wiring diagram the only load I saw that would activate on the brown was the neutral light. So I traced the heavy load down by switching on the key, pulling fuses one at a time and measuring the voltage at the switch brown wire (brown wire to ground). The headlight was already turned off, so pulling the headlight fuse was a nothing burger. Pulling the fuse for other components (horn, turn signal lights, etc.) didn't drop much at all. The ah ha moment came when I pulled the ignition fuse. Bam! Almost full battery voltage on the brown wire at the switch. So that is my source of voltage drop from loads in the system.

 

[Mashermoto]

Trying to think out loud
The frying of rectifiers and rotors Guessing the system is demanding output from the alternator to long and to high

As up here in north on 80 ies Suzukis starting in spring with low battery assuming the bike would charge up
Problem was the rectifier design was not such that it was able withstand any prolonged time Fried the regulator and then the alternator that was a PMA type I believe

So here the voltage drop 1.5 V might not be to high I dont know but can it be that there are some partial ground somewhere
the machine starts the regulator notices the system Voltage typically what is going to the battery ( across )
If that tends to be low the regulator rises the upside on the alternator trying to adjust up .But if there are this partial ground
or something uses to much fex Extra Headlights It is working the alternator at longer times at higher levels

Perhaps measure what goes through each fuse at power on -- se if something looks high
perhaps Smaller fuses in for test

The smaller fuses has the advantage that if it is a problem that come and goes the measurement wont show it cold but the smaller fuse catches it
when driving ..A voltmeter on the machine is a good thing to have.

Are the electrical specs for the coils suitable for the bike and pamco ?

Totally agree a volt meter is a good thing to have. During my first bout of charging issues I had to trailer the bike back home because I couldn't tell that the charging system was failing. So enough of that noise. I installed a volt meter and that is what saved my bacon with this recent bout of charging issues. Usually the volt meter would show 13-14v when riding and 12v at idle. When I noticed it wasn't moving past 12v I suspected something wasn't right. When it dropped to 11v I high tailed it home.

This is my volt meter. Reflections are a bit blurry but each light represents 1 volt. From left to right, 8 and 9v are red, 10-11v are yellow, 12v is green, 13-14 and 14-15 are different colors but I don't remember what they are. Super easy to read and comforting to know what your battery status is.

I wired it up so that it comes on when the key is turned on by using the black cube switch shown below. The trigger post is connected to my tail light wire, the power post is connected to the battery and the signal post straight across from the power post is connected to the meter. So the meter reads directly from the battery.

This cube switch was originally used as one of PamCo Pete's modifications to bypass what he called the "killer switch." He noted that a lot of XS650's would develop dirty contacts in the kill switch and would cause a loss of voltage to the ignition coils. So he came up with this solution to use the cube switch to bypass the kill switch and power the coils directly from the battery. I used it and it worked. But later Pete recommended not using it because if the battery voltage ever dropped to 9v for some reason the cube switch would not function and leave you stranded. So I took it off. Later as I was trying to figure out how to connect the volt meter directly to the battery and still be able to switch it on and off by using the key, I found this to be a good solution.

 

[Mashermoto]

Was trying to keep it in simple terms.

Yeah Artic. What Jim said

 

[Mashermoto]

I think where it stands is to not worry about the load draw from the coils for now. When I get the rotor back from Jim I'll get the charging system working again and do some more testing. There are one or two other issues I observed but let me see if getting the charging system functioning again will clear those problems.

I can say the aftermarket replacement rotor had the charging system working well before the rotor coil wire came loose. I'll cross my fingers that nothing else was an issue.

 

[Mashermoto]

Totally agree a volt meter is a good thing to have. During my first bout of charging issues I had to trailer the bike back home because I couldn't tell that the charging system was failing. So enough of that noise. I installed a volt meter and that is what saved my bacon with this recent bout of charging issues. Usually the volt meter would show 13-14v when riding and 12v at idle. When I noticed it wasn't moving past 12v I suspected something wasn't right. When it dropped to 11v I high tailed it home.

This is my volt meter. Reflections are a bit blurry but each light represents 1 volt. From left to right, 8 and 9v are red, 10-11v are yellow, 12v is green, 13-14 and 14-15 are different colors but I don't remember what they are. Super easy to read and comforting to know what your battery status is.
View attachment 364412

I wired it up so that it comes on when the key is turned on by using the black cube switch shown below. The trigger post is connected to my tail light wire, the power post is connected to the battery and the signal post straight across from the power post is connected to the meter. So the meter reads directly from the battery.
View attachment 364413

This cube switch was originally used as one of PamCo Pete's modifications to bypass what he called the "killer switch." He noted that a lot of XS650's would develop dirty contacts in the kill switch and would cause a loss of voltage to the ignition coils. So he came up with this solution to use the cube switch to bypass the kill switch and power the coils directly from the battery. I used it and it worked. But later Pete recommended not using it because if the battery voltage ever dropped to 9v for some reason the cube switch would not function and leave you stranded. So I took it off. Later as I was trying to figure out how to connect the volt meter directly to the battery and still be able to switch it on and off by using the key, I found this to be a good solution.

I forgot to mention about the coil question. I think it is okay for the PamCo ignition. The coil was originally specked by Pete when he was helping me build the Gerber ignition. I think I asked him about that when he sent me one of his Pamco ignitions, but I really don't remember. It is a high output coil, but it is basically two 3 ohm single fire coils in one mold. I believe that is what everyone is running with the PamCo setups except that most setups have individually mounted coils. I'll have to look into that.

 

[Jim]

I can say the aftermarket replacement rotor had the charging system working well before the rotor coil wire came loose. I'll cross my fingers that nothing else was an issue.

I'd agree with that. Those aftermarket rotors don't have a good track record. We had someone here shortly after I started rewinding, burnt up 3 Chinese rotors in about 200 mi he said. Rewound his original and no worries after that.

 

[Signal]

A couple of thoughts that will hopefully add clarity rather than confusion.

• The photo of the second failed rotor looks in the photo to be a mechanical failure rather than overheating.
• Possibly the lost 1.5 volts is also seen by the voltage sensing circuit of the regulator causing it to think it needs to keep the rotor energised longer.

Here is a terribly drawn diagram of the fix to stop the relay leaving you stranded. In my defence it was only a note intended for myself.


It is basically 2 supplies to the ignition coils with a diode to stop the relay latching and making the other switches unable to shut the motor down.

The downside is you wont know the relay has failed and if it does you will also lose the forward bias of the diode 0.7V as well as the switch losses.

Maybe the resultant change in starting/running of the bike will tip you off something is up.

 

[Mashermoto]

I forgot to mention about the coil question. I think it is okay for the PamCo ignition. The coil was originally specked by Pete when he was helping me build the Gerber ignition. I think I asked him about that when he sent me one of his Pamco ignitions, but I really don't remember. It is a high output coil, but it is basically two 3 ohm single fire coils in one mold. I believe that is what everyone is running with the PamCo setups except that most setups have individually mounted coils. I'll have to look into that.

Yep. 2.5-5 ohms is what is recommended by Pete for the PamCo. 3 ohm coils are readily available and most commonly used.