Expanded charging system guide (In progress)

We are from different worlds. In my world compressed air doesn't clean. It blows. Especially little stuff into small orifices that plug up said orifices. So now you have a compromised fuel mixture along with any other problem you were trying to eliminate.
 
Well with a fully charged battery from a shore charger she'll run well for a at least a few minutes maybe 1/2 hour with the headlight off. At this point you should have a volt meter you can see while riding.
 
Thanks for the reply Gary,

I did check the alternator brushes in the stator, could me putting these back in incorrectly cause a misfire?

Is it worth disconnecting the reg/rec and seeing if the misfire goes away?

The bike is idling okay, just misfiring with revs, does this mean coils are okay? I read this in another thread.

If I do want to replace these BS38 carbs with something different, what are my options?
 
No, still not resolved. Hence my comment about the misfiring possibly being a symptom of a failing charging system? The misfiring started instantly as I was riding back from getting some lunch, and I haven't been able to resolve it.

I am waiting on alternator brushes. I fixed the dodgy connection to the rectifier as we discussed and am getting battery voltage at the red wire now. Still no charging.

I tried to disconnect the rectifier to do the 12-part rectifier test but couldn't get it off the frame of the bike (i'm thinking a 40 year old seized bolt might do that!), and haven't had a minute to try again. I'll blast it with some Inox and try again. Any tips?

I'm a little confused by Curly's guide Vs what has been said in this thread. On one hand, the slap test is supposed to tell you that your rotor and brushes are working. But in my case, I passed the slap test but have a 7mm (very worn) alternator brush?
 
Yeah, misfire could be caused by low battery voltage.
Best to resolve that first.

The short brush is at its replacement limit, but it's still working. Slap test OK.

You can test the rectifier without removing it. Just probe into its connector.

FYI, the 'unplug regulator' test is only for 80-83 TCI ignitions...
 
Thanks mate, I'll probe into the connector when I get home and will tell you my findings. But if you're only probing into the connector, how do you test the actual rectifier itself? That is, the 6 diodes etc.
 
Here's the charging system schematic for the 70-79 models:
ChargingColor3.jpg


Here's the charging system description for the 70-79 models:
XS650-3PhaseCharging.jpg


Here's a blowup of the rectifier. We'll use this to describe the rectifier tests.
XS650-Rectifier.jpg


Set your meter to test resistance, on the 2K (2000 ohm) scale. On many meters, this position is also the diode test. If your meter uses unpluggable testleads, be sure the red testlead is in the (+) socket, black testlead in the (-) socket.

The rectifier must be unplugged from the harness for these tests.

First, the forward conduction tests:

For the ground-side diodes:
Clip the red testlead to the rectifier's negative (black wire) connector.
Using the black testlead, test each white wire connector (3 individual tests).
Meter should show some conductivity. If diode test feature exists, should show about 0.600-0.700.

For the hot-side diodes:
Clip the black testlead to the rectifier's positive (red wire) connector.
Using the red testlead, test each white wire connector (3 individual tests).
Meter should show some conductivity. If diode test feature exists, should show about 0.600-0.700.

Next, the reverse-bias (no conduction) tests:

For the ground-side diodes:
Clip the black testlead to the rectifier's negative (black wire) connector.
Using the red testlead, test each white wire connector (3 individual tests).
Meter should show no (zero) conductivity.

For the hot-side diodes:
Clip the red testlead to the rectifier's positive (red wire) connector.
Using the black testlead, test each white wire connector (3 individual tests).
Meter should show no (zero) conductivity.

That's the complete 12 test procedure. If any value is incorrect, the rectifier is bad.
 
TwoManyXS1Bs said:
Here's the charging system schematic for the 70-79 models:
View attachment 60746

Here's the charging system description for the 70-79 models:
View attachment 60747

Here's a blowup of the rectifier. We'll use this to describe the rectifier tests.
View attachment 60748

Set your meter to test resistance, on the 2K (2000 ohm) scale. On many meters, this position is also the diode test. If your meter uses unpluggable testleads, be sure the red testlead is in the (+) socket, black testlead in the (-) socket.

The rectifier must be unplugged from the harness for these tests.

First, the forward conduction tests:

For the ground-side diodes:
Clip the red testlead to the rectifier's negative (black wire) connector.
Using the black testlead, test each white wire connector (3 individual tests).
Meter should show some conductivity. If diode test feature exists, should show about 0.600-0.700.

For the hot-side diodes:
Clip the black testlead to the rectifier's positive (red wire) connector.
Using the red testlead, test each white wire connector (3 individual tests).
Meter should show some conductivity. If diode test feature exists, should show about 0.600-0.700.

Next, the reverse-bias (no conduction) tests:

For the ground-side diodes:
Clip the black testlead to the rectifier's negative (black wire) connector.
Using the red testlead, test each white wire connector (3 individual tests).
Meter should show no (zero) conductivity.

For the hot-side diodes:
Clip the red testlead to the rectifier's positive (red wire) connector.
Using the black testlead, test each white wire connector (3 individual tests).
Meter should show no (zero) conductivity.

That's the complete 12 test procedure. If any value is incorrect, the rectifier is bad.
Click to expand...

2M,

I unplugged the rectifier from the harness. I don't have alligator clips so I was just touching the probes where you told me to clip them, annoying, but the same thing right? I also assume that you were instructing me to test the connectors in the rectifier side of the harness?

My multimeter has a diode test function, so I used that.

First, the forward conduction tests:

For the ground-side diodes:
0.465
no conductivity (open loop reading)
no conductivity (open loop reading)

For the hot-side diodes:
0.475
no conductivity
no conductivity

The reverse-bias tests:

For the ground-side diodes:
no conductivity (open loop reading)
no conductivity (open loop reading)
no conductivity (open loop reading)

For the hot-side diodes:
no conductivity (open loop reading)
no conductivity(open loop reading)
no conductivity(open loop reading)

So, my rectifier is cooked!

Thanks a lot 2M, there is no way I could have diagnosed this without you. Can you point me in the right direction for a part number or link for a decent replacement.

I know I can make one using two full-wave bridge rectifiers and a piece of aluminium, but at this stage, I'd rather just buy. This bike has been off the road long enough now.
 
Last edited:
louis said:
Quick update, still waiting on some parts. Bike is now misfiring badly when I ride it. I pulled the carbs and cleaned the jets with compressed air and it's still misfiring.

I'm assuming that the bike is now finally running like youd expect with a failing charging system. I read a quote from retired gentleman in another thread, "forget the carbs and fuel system until you sort out your charging". Seems like solid advice.
Click to expand...

2M is giving you good advice.

Yes, you must always sort out the charging system first. Otherwise you will just go around in circles and solve nothing.

On these old bikes, its really not worth speculating if the stock rectifier is bad, or if the regulator is bad. They are both of an old design and they are both worn out. Its false economy to try to keep using them.

Always buy new brushes, so you know what you are working with. Clean the slip rings so they are shiny. Buy a new 3 phase rectifier, similar to what 2M pointed out (25 amp or larger work just fine). Buy a nos automotive regulator such as the VR-115 from E-bay.
Here's the link with the details:
http://www.xs650.com/forum/showthread.php?t=21485

Once you have the new rectifier and regulator installed, and the wiring checked over, you want to confirm you are able to get to 14 to 14.5volts when you rev up to 3000+ rpm.

Now with the charging system working 100%, you can continue on chasing other problems that may be fuel/carb related.

Highly recommended..........................replace the stock taillight with a LED taillight, as it reduces current required from the alternator, and aids voltage even at idle. Install a voltmeter on your bike, so you can see it as you ride.
 
Okay, you'd still replace the regulator even though it tested okay?

Is that just because it's outdated technology and is making the rest of the charging system work harder than it needs to?

Just ordered a rectifier and VR115 regulator, out of pocket about 40 US dollars. Mike is asking 102 for his plus it'd be 25 to ship it to me.

Now I just need to make sure my complete novice wiring skills are up to par.
 
louis said:
Okay, you'd still replace the regulator even though it tested okay?

Is that just because it's outdated technology and is making the rest of the charging system work harder than it needs to?

Just ordered a rectifier and VR115 regulator, out of pocket about 40 US dollars. Mike is asking 102 for his plus it'd be 25 to ship it to me.

Now I just need to make sure my complete novice wiring skills are up to par.
Click to expand...

Yes, absolutely replace the old stock regulator. Sure it probably still works, but may not work very well. It contains springs that lose their tension over the years, and it contains mechanical contacts that get oxidized and increase resistance. The charging voltage would likely have a large variation as rpm changes, and would never reach 14+ volts. The VR-115 is so cheap to buy, that its a "no brainer". I've used the VR-115 for many years now, and my voltage gauge on my bike, always sits at 14.2 volts as I drive down the highway.

A modern 3 phase rectifier is also a huge improvement over the old stock design.

Both my stock rectifier and stock regulator were working when I removed them from my bike. They now sit on a shelf in my basement where they belong. They are suitable as museum pieces, but nothing else.

Can other lads continue to use the old stock rec and reg? Of course they can, but they will have to fiddle with adjustment screws on the reg, and their batteries will never be fully charged. They will complain that the stock alternator is a piece of crap, and likely spend hundreds of dollars on replacement parts that they don't need to.
 
Without wanting to get too controversial, does that mean that most of the people that replaced their stock charging system with a PMA didn't really need to?

Was having this discussion with a local 81 XS owner the other day and he was adamant that these charging systems needed to be replaced with a PMA or similar.
 
louis said:
Without wanting to get too controversial, does that mean that most of the people that replaced their stock charging system with a PMA didn't really need to?

Was having this discussion with a local 81 XS owner the other day and he was adamant that these charging systems needed to be replaced with a PMA or similar.
Click to expand...

Too late..................you've now caused controversy:D

Over the years, I've heard the statement many, many, times, "The stock charging/alternator must be replaced by a PMA". Most of the people that say that, have no knowledge, and no training on electrical equipment. Its another internet myth that gets repeated over and over, so many thousand times, that it must be true:doh: The PMA sellers encourage this by heaping lots of hyperbole on their websites, while they make large profits from naive buyers.

The stock alternator is a high quality Japanese made product. The fact that my bike is still using the original stock alternator stator and rotor, is testament to its superior longevity. On the 1970 to 1979 years, the stock rectifier and regulator, while good when they were relatively new, have not aged well, and are best replaced with more modern units.

Do the stock rotors and stators fail? Yes, of course they do, as all electrical equipment will fail over time. Over the past 9 seasons, I keep expecting my stock alternator rotor or stator to fail, but they just keep running with no problems at all. I even keep a spare rotor in my basement, ready for that dreaded, fateful day when my charging system dies:yikes:

Most charging problems are due to brushes that are too short, oxidized connector contacts causing high resistance, and guys trying to charge dead batteries. In other words..............if you never do any maintenance on bikes/cars/trucks etc., you will eventually have electrical problems, and then complain that the vehicle is of poor quality.
 
Replaced alternator brushes. Took off LHS cover and cleaned up everything and cleaned up clutch mechanism.

When trying to clean battery strap to starter relay the plastic has snapped off the top and now I can't get a ground and it's blowing fuses. Do I replace the starter relay or can I ground it somewhere else?

Still waiting on my rectifier and regulator. Ah the joys of living at the bottom of the earth
 
The only REAL advantage a PMA system has is you can run without a battery. Anything anyone says otherwise is just hype.
Leo
 
louis said:
Replaced alternator brushes. Took off LHS cover and cleaned up everything and cleaned up clutch mechanism.

When trying to clean battery strap to starter relay the plastic has snapped off the top and now I can't get a ground and it's blowing fuses. Do I replace the starter relay or can I ground it somewhere else?

Still waiting on my rectifier and regulator. Ah the joys of living at the bottom of the earth
Click to expand...

I'm not clear on what you mean "plastic has snapped off".............which plastic is that?

What ground are you trying to get???
Can you post a picture showing the problem area?

With the cleaning you did, perhaps you disturbed the wiring harness that runs from the alternator to the harness. Look closely to see if there are any bare wires that may touching ground blowing a fuse.
 

Similar threads

G
Weak charging system or mechanic with weak skills?
2
Replies
23
Views
1K
Jim
Jim
E
Question about rotor and charging.
2 3
Replies
41
Views
2K
Eric12171
E
L
Yet another charging thread :)
2
Replies
22
Views
420
Lou_TX
L
I
Pre recommissioning electrical checks?
Replies
13
Views
472
Its been a long time
I
JNaw
Rotor melted itself 500km after rewind?
Replies
15
Views
385
JNaw
JNaw
Back
Top