82 XS400SJ Charging system nightmare

[Ebola Monkey]

I put a brand new battery in the bike, and I get almost 14V across the battery terminals but then it drops off after a while.

If I let it run for a while it flattens out at about 12.7V at idle, and 13V at 3,000 RPM.

I'm trying to test everything out, but I'm not sure if I'm Going about it right. I have the xs360-400 PDF Manual which is incorrect on a number of things.

Field Coil/Armature Tests

I tested the Field Coil/Armature according to the 76-82 xs360-400 manual PDF

First test:Resistance between 3 white leads (Armature)

• Should be 0.72 ohms +/- 10%
  
• Results: 1.0 - 1.1 ohms.
  
• According to the manual the armature wiring is likely broken, and it must be replaced.
  

Second test:Field Coil Resistance Manual says the leads are Green-Green, actually Green-Black on my bike.

• Should be 4 ohms +/- 15%
  
• Results: 3.4 ohms
  
• So it's right at the low end.
  

Regulator Testing

The manual I have says "A mechanical voltage regulator is used on all models". This is not true. My bike has a solid state regulator, so I can't test it according to the manual.

CMSNL lists the same part number for for the 1978-1982 xs400, but shows a mechanical one on some, and solid state on others. Any information on my actual regulator is long gone.

Rectifier Testing

I tested the Rectifier with These instructions: http://www.cyclewareables.com/pages/electrical_test_images/stator3_test3.jpg

First test:

• Meter Red to Rectifier Red
  
• Meter black to Rectifier White (x3)
  
• Result:No reading
  

Second test:

• Meter BLACK to Rectifier Red
  
• Meter RED to Rectifier White (x3)
  
• Result:.53V - .545V
  

Third test:

• Meter BLACK to Rectifier BLACK
  
• Meter RED to Rectifier White (x3)
  
• Result:No reading
  

Fourth test:

• Meter RED to Rectifier BLACK
  
• Meter BLACK to Rectifier White (x3)
  
• Result:.53V - .545V
  

I tested 2 rectifiers and both had similar results. The first results are above, and the second was in .51V-.53V range. According to this test, they both fail.

Then I tested it as described in the 76-82 xs360-400 manual PDF. I get readings of ~2.4M ohms going one way, and nothing going the other. Does this sound right?

Which test should I trust?

So where I stand is:

• The armature is out of spec according to my manual that I can't really trust.
  
• The field coil is just barely in spec according to my manual I can't really trust.
  
• The Rectifier is out of spec according to a random test I found through this forum.
  
• I think the rectifier is good according to my manual I can't trust.
  
• My voltage regulator is mechanical according to my manual which I can't trust, while it's solid state in the real world. So I don't know how the heck to test it.
  
• I am frustrated beyond belief by this whole situation. I can't find the CORRECT manual online (1975-1984 xs250 - 360 - 400), and honestly don't want to fork over a bunch of money, and wait for a week for a manual that might not be any more help than what I have.
  

[exess4]

[*]The Rectifier is out of spec according to a random test I found through this forum.

Noviced newb here , my "member" status should read "pre-ignition", I posted that random test link and it is not model specific or anything so figure manual might be more trustworthy. I'll lay low and just listen for now.

[drewpy]

14v @ 3k revs is within spec.

with these bikes, you need a good battery, if it's not holding charge then you wan't get back a decent charge!!

the tesing of the solid state voltage regulators only states the above test (14v - 14.7v) with a fully charged battery.

rectifiers are diodes which only allow electricity to flow in one direction. this process converts AC current to DC, that is why you won't get a reading one way.

I'd check battery condition firstly

NEVER RUN ENGINE WITH BATTERY DISCONNECTED!

drewps

BTW I just posted a link for a parts book for the SJ under xs400 links

[Ebola Monkey]

Thanks for the reply drewpy.

I'll take the battery in to get it tested. I really hope that's the problem even though I already lost the receipt (it's only a week old).

Like I said, I think the rectifiers might be ok, and I've got another regulator on the way. The previous owner was obviously trying to track down the problem because there were 2 rectifiers on the bike (1 wired, 1 not), the regulator had a piece of tape on the bottom that read "Yamaha 400", and there was an extra starter in the saddlebag.

I've got a bad feeling that it's going to be in the generator, and probably the armature. Simply because it should have ohmed out at .65 - .79, and actually ohmed out at 1 - 1.1.

[Karen_Agusta]

Your tests sound good

Also what Drewpy said is important

Never run a solid state machine on a disconnected battery

As far as batteries go I wrote a small post on them if you want to read it

Here is the link ...

Though from your tests I would tent to agree with you it could very well be the generator

.

Rubber Side Down

.

Karen

Thanks for the reply drewpy.

I'll take the battery in to get it tested. I really hope that's the problem even though I already lost the receipt (it's only a week old).

Like I said, I think the rectifiers might be ok, and I've got another regulator on the way. The previous owner was obviously trying to track down the problem because there were 2 rectifiers on the bike (1 wired, 1 not), the regulator had a piece of tape on the bottom that read "Yamaha 400", and there was an extra starter in the saddlebag.

I've got a bad feeling that it's going to be in the generator, and probably the armature. Simply because it should have ohmed out at .65 - .79, and actually ohmed out at 1 - 1.1.

[Ebola Monkey]

Well, I had never thought to use the REL mode on my meter to test the generator. I read on a 650 forum that you have to take into account the meter lead resistance which is .3 ohms on my meter.

This puts all 3 wires from the stator at .7-.8 ohms which is where it should be.

Now I'm even more confused.

[exess4]

rectifiers are diodes which only allow electricity to flow in one direction. this process converts AC current to DC, that is why you won't get a reading one way.

This is true, since mine failed on simple continuity test with no current in EITHER direction. But good luck on the real problem.

[Ebola Monkey]

Got the new regulator today, and it ohmed out the same as the old.

Here's what I got tonight on a freshly charged battery (starting at 7:00pm):

• 13.6 volts @ 1200 rpm
  
• 14.3 volts @ 2000 rpm
  
• 13.1 volts @ shut down
  
• 12.7 volts @ 12:15am (~3hrs after shut down)
  

I'll post the readings in the morning.

[drewpy]

Got the new regulator today, and it ohmed out the same as the old.

Here's what I got tonight on a freshly charged battery (starting at 7:00pm):

• 13.6 volts @ 1200 rpm
  
• 14.3 volts @ 2000 rpm
  
• 13.1 volts @ shut down
  
• 12.7 volts @ 12:15am (~3hrs after shut down)
  

I'll post the readings in the morning.

that sounds right

[Ebola Monkey]

that sounds right

This morning:

• 12.3 Volts @ 11:00 am 11 hours after the last shut down
  
• 12.7 @ 1200 rpm
  
• 13.6 @ 2000 rpm
  

I worked on the bike for a couple hours today. I wired up new rear signals, and used a trailer adapter as a run/turn/brake adapter.

Started it up again, but the starter struggled. Took a good 30 seconds or so.

It struggled to get up to 12.5 at idle, and would drop off big time when I hit the brakes, or used signals.

I just restarted it, and here's the results:

• 12.3 Volts 10 minutes after last shut down.
  
• 11.9 Volts with key on
  
• 12.1 Volts @ 1200 rpm
  
• 11.8 Volts @ 1200 rpm with brakes on
  
• 12.2 Volts @ 2000 rpm
  
• 12.5 Volts @ 3000 rpm
  

I know the blinkers, and brake light would make the headlight dim before. There were no rear blinkers then. Now with the rear running lights/blinkers it's even worse. When one blinks on, the other blinker, and the brake light dim so bad it's hard to tell which signal is on. The headlight also dims bad.

The only thing that's more than stock is the rear signals as running lights. The electrical system has to be able to handle the extra draw of those. I won't be able to get the battery tested until tomorrow at the earliest.

[Ebola Monkey]

Well, it just keeps getting worse.

I had the battery checked out, and it tested out fine. Like I mentioned it's only a week old.

I also got my Yamaha service manual in the mail. It also says that the voltage regulator in mine is the mechanical one, while the reality is it's solid state.

So where I'm at right now is:

• Rectifier seems to test out OK
  
• Stator seems to test out OK
  
• Field Coil seems to test out OK
  
• Battery tests out good
  
• Don't know how to test the solid state regulator, but I've tried 2 with the same results.
  
• On a freshly charged battery it throws 14+ volts, but every time I shut it down, start again it loses voltage.
  

[Speedshop]

This model is suspectable to damage to the wiring from the gerenerator in the area around the sprocket/gear change.

You need to remove the wiring to fully inspect all areas(unplug the connectors but leave the generator fitted so you can move and see all areas of the loom) make sure you clean the loom in this area. If the outter sleeving is damaged you will need to open it up and inspect all the wires for damage and chaffing.

50% of charging problems on these are caused by damaged wiring here.

Have you set the meter to diode testing when checking the rectifier?

It makes no difference if you have a solid state regulator fitted, I routinely binned the older sort and fitted the late type when i worked in the bike shop.

[Ebola Monkey]

Im confused on testing the rectifier.

When I test it according to my service manual it says:

• Connect Tester + to rectifier +, and Tester - to rectifier U,V,W and should have continuity. My meter shows NOTHING
  
• Connect Tester - to rectifier +, and Tester + to rectifier U,V,W and should have DIScontinuity. My meter shows 3.0M ohms roughly on every one.
  
• Connect Tester - to rectifier -, and Tester + to rectifier U,V,W and should have continuity. My meter shows NOTHING
  
• Connect Tester + to rectifier -, and Tester - to rectifier U,V,W and should have DIScontinuity. My meter shows 3.0M ohms roughly on every one.
  

So my results are the exact opposite right? This is on the Ohms setting on my meter.

When I test it out on the diode setting I get:

• Meter + to Rectifier + Meter - to U,V,W I get NOTHING
  
• Meter - to Rectifier + Meter + to U,V,W I get .5V
  
• Meter - to Rectifier - Meter + to U,V,W I get NOTHING
  
• Meter + to Rectifier - Meter - to U,V,W I get .5v
  

Again, + to + and - to - I get nothing, but + to - and - to + I get .5v across all 3 wires.

Am I missing something here, or does this all sound right?

I charged up the battery again, and monitored the voltage again.

Headlight connected:

12.25v @1200 rpm

12.70v @2000 rpm

13.00v @3000 rpm

Headlight disconnected:

12.5v @1200 rpm

13.0v @2000 rpm

13.2v @3000 rpm

Basically I can start out with a fresh charge, and push good voltage, but with the lights on, and everything it can't keep up and settles in with the numbers above.

Unless it's only a couple minutes after shutdown the starter is useless. It will turn and turn, but won't start. If it's not completely cold it will start on 1 kick.

[Speedshop]

That rectifier is OK. 3meg ohm is considered no continuity, although I'd expect to see 7 meg, but if all the readings are the same I'd say that's good to go.

A .5 volt on diode test is about right, it should be .6 so I'd guess your meter is off. If it cost less then £100 and hasn't been calibrated your meter not being accurate is more likely then 6 diodes having failed to give the same readings.

Leave the rectifier alone now and turn your attention to another part of the system!

There is most definately not enough of a difference in voltage between engine off and charging. You need to see about 14.5 to 14.7 volts with it charging and head lamp on.

What is the resistance of the FIELD winding? If it is less then stock I'd say that's your problem.

What should the resistance of this winding be? And what is yours?

[Ebola Monkey]

That rectifier is OK. 3meg ohm is considered no continuity, although I'd expect to see 7 meg, but if all the readings are the same I'd say that's good to go.

A .5 volt on diode test is about right, it should be .6 so I'd guess your meter is off. If it cost less then £100 and hasn't been calibrated your meter not being accurate is more likely then 6 diodes having failed to give the same readings.

Leave the rectifier alone now and turn your attention to another part of the system!

There is most definately not enough of a difference in voltage between engine off and charging. You need to see about 14.5 to 14.7 volts with it charging and head lamp on.

What is the resistance of the FIELD winding? If it is less then stock I'd say that's your problem.

What should the resistance of this winding be? And what is yours?

Thanks for the reply.

The field coil should be 4Ω ±15% Mine is at 3.4Ω which is right at the bottom end.

I have (2) regulators that both ohmed out the same, (2) rectifiers that both ohmed out the same, (2) stators that both ohmed out the same, and (2) field coils that both ohmed out the same. These are all used. The extra rectifier was on the bike, the regulator I bought off ebay (stock regulator was already replaced), and the stator, and coil were a surprise in a parts lot I bought.

I think the previous owner was trying to track down this problem, and failed. Like I mentioned the Regulator, and Rectifier were already replaced. The headlight was also on a switch when I bout it. I assumed it was because the diode on the headlight circuit had shorted out, and previous owner hadn't found it. May have been been, but may have also been because it was a drain on the system.

The only other thing that I've noticed on the bike that is not right is 1 resister cap is leaking. It tests out at 10kΩ, but if I touch it with the bike running I'll get a shock. I verified it is the problem by switching the ccap to the other cylinder, and got the same result. This couldn't effect the charging system could it? The other cap ohms out at like 3MΩ.

My meter is a Fluke 83 III, so not a cheap meter, but never been calibrated. Ive had it for years, but looks like new. I take good care of it. Will look into getting it calibrated though.

[Speedshop]

A fluke is a good meter so should be OK, but they can go out.

I'm assuming you replaced the burnt out diode?

When you turn on the ignition you get the full battery voltage down at the generator end of the field winding? it should not be more then .5 volt different from the battery.

With the engine running and the 3 phase output connected to the rectifier you see the same AC value on each of the phases? rev the engine as well and note the change.

When you switch the bike off and connect the meter in current mode, in series with the battery negative lead and the battery there is 0 current flow?

[Ebola Monkey]

A fluke is a good meter so should be OK, but they can go out.

I'm assuming you replaced the burnt out diode?

When you turn on the ignition you get the full battery voltage down at the generator end of the field winding? it should not be more then .5 volt different from the battery.

With the engine running and the 3 phase output connected to the rectifier you see the same AC value on each of the phases? rev the engine as well and note the change.

When you switch the bike off and connect the meter in current mode, in series with the battery negative lead and the battery there is 0 current flow?

Yeah, did replace the diode.

I load tested it today, and got no load with the key off, and 4.25V with the key on.

Now for the voltage readings:

Idle:

Battery: 12.25V

Generator: ~10.6V on all 3 legs

Field Coil: 10.35V <<seem odd?

2,000 RPMs:

Battery: ~13.5V

Generator: ~12.5V on all 3 legs

Field Coil: 12.25V <<seem odd?

2,500 RPMs:

Battery: 13.5-14V

Generator: ~13V on all 3 legs

Field Coil: 8.8V <<seem odd?

All of the voltage readings fluctuate a bit, and will vary because I would do 1 @ all RPM ranges, then the next. I never got above 14.15V or so, and it would fall below 14 if I stayed above 2500RPMs or so.

It seems to be keeping up (not great) as long as I don't turn on the blinkers, or brake lights while idling. When I do it drops voltage, and can't seem to catch up.

I have another field coil, but it's well used, and ohms out almost identical to the one that's on the bike now.

My replacement plug caps will hopefully be in by Friday.

The service manual isn't very explicit about replacing the stator, and field coil. Is that area filled with oil? Do I need to replace gaskets if I open it?

Thanks Again For The Help

[Speedshop]

There's your problem - that field voltage is all over the place. Check the wiring very carefully between the regulator and the generator (i think i read you changed the regulator). I've pointed out that these used to wear through the generator wiring at the gear lever so if you haven't already checked - please do so. My old black SE did exactly this and I saw several other 400s that did the same.

The generator readings are low, they are normally much higher direct off the generator say about 20 volts rising to 50. The meter needs to be on AC. These readings would be low if there was a fault with the field. Which is I think what you are looking at.

You need to see full battery voltage on the field with just the ignition on. For it to drop to 8.8 volts I'd want to be seeing 14.5 or higher across the battery.

Can you confirm you have a solid state regulator and you've tried different ones? If its vibrating contacts, run some 1200 grade through the contacts and re-check.

Its been 20 years since I last owned a 400, can't remember if the generator sits in oil, but there will be a gasket to seal the cover to the engine either way.

My XS650 stopped charging last year, the field winding should have been 5 ohms, but measured 3.5, it was the field windings that was the cause - very common on the 650, I'd check for a wiring fault on the 400 first.

[Ebola Monkey]

There's your problem - that field voltage is all over the place. Check the wiring very carefully between the regulator and the generator (i think i read you changed the regulator). I've pointed out that these used to wear through the generator wiring at the gear lever so if you haven't already checked - please do so. My old black SE did exactly this and I saw several other 400s that did the same.

The generator readings are low, they are normally much higher direct off the generator say about 20 volts rising to 50. The meter needs to be on AC. These readings would be low if there was a fault with the field. Which is I think what you are looking at.

You need to see full battery voltage on the field with just the ignition on. For it to drop to 8.8 volts I'd want to be seeing 14.5 or higher across the battery.

Can you confirm you have a solid state regulator and you've tried different ones? If its vibrating contacts, run some 1200 grade through the contacts and re-check.

Its been 20 years since I last owned a 400, can't remember if the generator sits in oil, but there will be a gasket to seal the cover to the engine either way.

I do have a solid state regulator, and have tried another one. I've also recently replaced many of the connectors including the ones to the generator, regulator, and field coil, so I know they are good. I haven't dug in to see where the wires go into the case yet, but that will probably be the next step.

Hopefully someone else remembers if it's going to be filled with oil before I dig in.

Hopefully someone else remembers if I'm in for an oily mess or not.

[tudor55]

There is a diode under the seat that controls the voltage to your battery if its weak or gone it will not charge!