Yet another charging issue...

rugbywarrior89

rugbywarrior89

Need more time...
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So I have been trolling around lately and trying everything to get my bike 82 heritage special SOHC to charge again. Last year, I was getting decent voltage but not the best (up to 13.8 volts) then all the sudden I started it this spring and it just stopped charging.

I did the rewire of both coil and stator
changed the voltage regulator
tested the rectifier
White wires showed a consistant 1.3 ohms not accounting for meter loss so thats good
green and black wires showed 4.5 ohms so thats good.
I was able to get blade to stick

Here whats strange. I tested the AC current coming out of my white wires while running and I got 10V, 10V, 1.5V. I'm not sure what the voltage is supposed to be but I'm sure they are supposed to be the same.:shrug:

I'm pretty sure my VR is working because I would lose voltage when I disconnected so I assume when I connect it, it's reading low voltage and completing the circuit. The bike acted the same way when I bypassed the VR as well. My system is producing about .2V DC hooked up at the moment.

I'm thinking that my stator windings are bad but I'm really not sure. I have never noticed anything wrong with them the multiple times I've had them out but sometimes you can't really see problems like that. Buying a new stator seems to be the next logical choice. Any idea?
 
rugbywarrior89 said:
Here whats strange. I tested the AC current coming out of my white wires while running and I got 10V, 10V, 1.5V. I'm not sure what the voltage is supposed to be but I'm sure they are supposed to be the same.:shrug:
Click to expand...
Did you unplug the multi point connector when you tested? With the stator connector unplugged from the harness you should see at least 75VAC at all three legs at 5000RPM. You will see less voltage at or near idle. BTW don't run the engine unplugged unnecessarily, do your test and reconnect the connector.
 
I did disconnect the connector to test it and plugged it right back in. wow, 10 V is not even close to 75. Now I definitely think the stator coil is bad. I guess it's back to ebay for me.
 
It sounds like your stator is cooked. Another test you can do is check to see if the stator has gone to ground. Set your meter to ohms and put one lead on the white wire and the other to ground. Do all three wires separately and see if there is a path to ground.
 
That would make sense that its grounding out. I bet it would be on the wire only getting 1.5V. Although theoretically, if there is continuity between all 3 wires, shouldn't they all be grounding if one is? Maybe I somehow touch the wire to the case when I rewired. I'll pull it apart tonight and see what I find.
 
Modern multimeters are effectively useless at measuring such low resistance - the best way to determine if you have a short somewhere in the stator is to run a known current through the wires (I like 10A because it makes for easy resistance calculations) and look at the voltage drop across the wires.

The spec for the stator is 0.49Ohm (490mOhm). So running 10A current through any of the two phase wires should have a voltage drop of 4.9V. Now the trick is basically getting a power supply that can do 10A - which I realize not many people have, but you may know someone that has one that you can use! It doesn't have to go to 10A, but I'd recommend at least 5A to get a good measurement resolution. Don't use a battery..

Based on your AC voltages while running - you were properly measuring AC voltage on your meter I assume - you've got some kind of short happening. Specdog has a great suggestion of measuring the coil relative to ground - do this when it's not plugged into the regulator.

I'd also inspect the phase wire connections on the stator themselves as well as the wiring harness to see if there's any shorting. Likely means taking everything out, but at least if you take it all out you'll be ready for a replacement :)
 
Modern multimeters are effectively useless at measuring such low resistance - the best way to determine if you have a short somewhere in the stator is to run a known current through the wires (I like 10A because it makes for easy resistance calculations) and look at the voltage drop across the wires.
Click to expand...

I agree but most failures I've seen usually aren't anywhere near .72 ohm between the white wire so as long as the ohms are low (<2ohm) and the same, I figure it checks out. Although I guess I may just prove myself an idiot when I get home tonight:wink2:

The spec for the stator is 0.49Ohm (490mOhm). So running 10A current through any of the two phase wires should have a voltage drop of 4.9V. Now the trick is basically getting a power supply that can do 10A - which I realize not many people have, but you may know someone that has one that you can use! It doesn't have to go to 10A, but I'd recommend at least 5A to get a good measurement resolution. Don't use a battery..
Click to expand...

Where did you get .49 ohm? Is that a difference between SOHC and DOHC? Also, what would you use for a power source. I am unaware of anything that I can my hands on easily that gives a constant DC current, except maybe a 24V battery and a capacitor maybe:confused:?
 
The dohc charging systems are not the same as the sohc ones. Whole different setup.
 
I just have a bunch of lab power supplies at work, and we deal with brushless 3 phase electric motors all the time, the principles of the charging system and our motors are basically the same with the exception that to vary the voltage the charging system varies the magnetic field strength of the rotor, where we have permanent magnets.

I got 0.49 from my '82 manual, DOHC - I realize now that this may not be applicable for you.. sorry!

As for getting your hands on a DC power supply, there are options, not all are good though. You could buy a cheap laptop power supply - get one that's 90W so it has the most current possible. Then what you'd need to do is hook it up and first measure the current flowing through the system (put your multimeter on 10A current mode, and put it inline with one side of the connection, in series, or you'll blow the fuse on the multimeter). Once you have that current and are satisfied with the current being constant, you can then reconnect it with out the multimeter and measure the voltage drop across the leads and divide this by the current to get the resistance.

I can't say for sure that would work, I would imagine some laptop supplies don't like to output current without a voltage present...

start with the visual inspection though I'd say..
 
Well I've got no continuity between the whit wires and ground. Looks like the stator is just shot. Oh well, Guess I'm getting a new one. Thanks for the help.
 
I disagree with robbiecampbellsoup on meters. Most any digital meter is plenty accurate for testing these systems. Even the ones from Harbor Freight. With the right coupon they are free.
When you do the testing on a low ohm reading, touch the probes together, this reading is the ohms of the test leads. Do the test, now subtract this test lead ohms from the test ohms. This gives you the actual reading.
My H/f meters check at about .7 ohms, my Sun Pro meter checks at .1 ohm. Test your stator, Lets say you get a 1.5 reading. With my H/F meter I would then subtract the .7 lead ohms, 1.5-.7=.8
Yamaha listed two specs for stators, some speced .9 ohms, some .49 ohms. I think they just listed the change with out telling about the change in method.
Some stators had a yellow wire that went to a safety relay. When measuring from thus yellow wire to each white wire you are measuring just one set of windings, thus the .49 ohms spec. Testing from white wire to white wire you are measuring two sets of windings, .49 x 2 = .98 ohms.
This is more than accurate enough for this. Doing a amp/ voltage drop thing is fine if you have the tools to do it. But why, When an almost free meter works just fine.
As mentioned the exact reading is not as important as all three be the same.
Also check from the three white wires to ground, the steel body of the stator.
On the XS400's the wires where they come through the housing often get chaffed, this lets the wires short to ground.
Inspect the wires to see if that's the problem.
On your field coil the 5 ohms is good, also check from the wires to ground.
Leo
 
So stupid me searched ebay for hours and still accidentally got an 82 Maxim stator instead :banghead:. It hasn't arrived yet to check it but can I make it fit? I know it probably can't but miracles do happen i guess. I feel so stupid...
 
This is definately the one I want right? He didn't give much info. I asked if he would do the ohm test but he hasn't responded yet? This is half the cost of any of the other ones I've seen. Do you think it's worth the risk? What are the odds that the stator would be bad (not counting the wiring of course. I will be changing that as a matter of principle anyways.

http://www.ebay.com/itm/1981-Yamaha...Parts_Accessories&vxp=mtr&hash=item46247efe4a
 
Looks like the motor had water in it because of all the rust around it. I would avoid that one unless he can give the you readings on it.
 
Have you called any of the local yards yet? I know of 2 in the Cleveland area, and I've bought parts from both for the XS400, so I'm pretty sure they have a few bikes being parted out. Might have what you need, and I always talk them down lower than what ebay parts sell for-

Cleveland Cycle and Salvage- 216-749-3979

Cycles R Us- 330 769 2629 (if you get a clueless person on the phone here, you can go to the actual yard in Medina on Saturdays and find the part yourself. Tons of neat stuff in that yard!)
 

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