New xs400 problems.

Before you start let's be clear. You are getting a measurement of 1.2 ohms on your meter from one white wire to another white wire? If so, that's fine and they're in good shape.

If you're only getting 1.2 volts ACV on your white wires to ground with the engine running, then they are damaged and you need to do what I list below...

from above posts I wasn't sure what your situation was.

First you remove the timing cover, which is on the left side, and says yamaha. 4 bolts.

I poked holes in a pizza box in the pattern the bolts were in on the side of the bike to keep track of where they go back to.

the clutch rod case comes off easily, just loosen the clutch cable at the adjuster nut on your handlebar before you take it off.

Once the clutch rod cover comes off, you'll see the chain sprocket, the yellow wire, the blue wire, and the wiring going into the stator and coil. If you see breaks at this point you're happy, but it often takes pulling off the stator cover too and looking at why there's a shortage. I had to cut off the shell around the bundled wiring, sort of a long sleeve of black pvc, that had hardened and cut my wires up, admitting oil and causing shortages.

back to the stator cover. Inside the timing cover you'll see the bolts holding the field coil in place. For now leave them attached. remove the bolts going around the stator cover and put them in the pizza box holes in the pattern that matches them on the bike. This is because they're not all the same length.

Cover your pipes with aluminum foil beneath the stator case so oil stays off them. If it smokes later you'll think you fried the bike and smoke needs to come from only one place. Put an oil pan or oil catcher beneath the timing cover area. It will drop a pint of old oil with the stator cover removed.

You'll need to pry up an edge of the stator cover because it's usually gasket sealed to the other half. Don't stress about the gasket, it's just a heavy paper template. You can make one after the stator cover is off the bike.

The stator cover indexes onto the bike with these large circular key pegs that are hollow in the inside. I pressed them onto the heavy paper to get an impression, cut out a hole the same shape, and then pressed the paper down over the cut holes onto the key pegs and traced the outer edges of the stator case to get my outer dimensions of my stator gasket. The inner I matched by taking the old pieces of the old gasket and laying them into the new outline I cut for the new gasket. New shape minus old shape equals gasket. Then put the gasket aside for later.

Get in there and make sure the wires are all intact and not touching each other or any oil if they are dented or dinged. If they are they will not measure the right ohms (1.2 to each other on white wires, no ohms when measuring white wires to engine or ground.)

The stator is stubborn and will not come out easily if you get it crooked. So inside the stator cover, you are going to undo the three bolts that hold it down and put them aside, as a group. label them.

The stator should stick up above the ridge it's bolted to the same amount all around. Make a depth measuring tool from a long thin piece of wire or something. Same height around is good. One high side is bad.
 
You da man! Appreciate the detailed how-to, just saw your write-up as well :thumbsup:. Im going to hopefully tackle this over the weekend so I will update when I dig into it.
 
Alright its been a while since I have had time to work on this thing. I was finally able to pull the cover off and check it all out. Everything looks pretty good except for the wiring, looks like it has maybe been repaired at some point as there is some electrical tape. Either way I might as well re-wire it all. What gauge wire do I need to use? Lowes has some 14g THHN but thats as small as you can get. Will this work?

On a side note here is my xj550 I have been working on too :thumbsup:.
 

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Alright I ended up just using regular 16g wire, soldered right outside of the grommet since the wiring inside the cover looked fine. Waiting for the gasket to dry, should be able to test it out tomorrow and see if I have any changes. I may go and buy a new battery as well since mine seems to be leaking acid.
 
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Alright started it up and it still is not charging. I was missing the frame ground from the battery so I added that hoping it would help but didn't seem to matter. checked the alt output wires and got the same results as last time. Tried adding direct 12v to the field coil and didnt notice any changes either. Bad stator/field coil?

Edit: After looking over the wiring diagram maybe I have the field coil wired up wrong? It looks like green feeds into black and brown feeds into green on the diagram. I have green to green and brown to black on the connector. Is this wrong?
 

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That diagram looks like it has a switched-ground field coil, in which case you'd need to short the green on the wiring harness to ground in order to bypass the regulator. You can double-check by putting a DMM up to the green while running and checking for voltage or ohms to ground.
 
I swapped the wires in the connector to the diagram specs. Still not charging, but I may still have a bad regulator I suppose. I hooked up my multimeter to the green and brown wire and I am getting power from both of them. So is the diagram right or wrong? In looking at the diagrams I have I don't see how the field coil gets grounded (if it even needs to, I don't know).

Edit: In switching wires back per this diagram I get the same results, both the brown wire and green wire are feeding power into the field coil.

I disconnected the plug while running and gave direct power to the green wire and grounded the black wire and I got a noticeable charge when I revved the bike. It went up to almost 13v, not great but it was a noticeable jump. I feel like im getting somewhere, what do I do next?
 

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Since the green is hot we know the regulator you have now is switched-source, which matches up with the 0volts you're reading from brown. The diagram you have shows brown being powered by the ignition switch, which is how I thought all of these bikes were setup. Just to clarify: was the bike running? Measure the voltage of the brown at another place on the harness, to make sure that you don't have a bad wire. If that turns out to be the case, then you will still need a switched-ground regulator to get the system working. I don't think the polarity of the wires on the field coil makes a difference, since it should only determine the phase of the alternator output, so I think you can hook it up directly to the battery terminals in order to bypass all of these gremlins. That should at least tell you what part of the system to look at next.
 
Sorry I edited my post a couple times after double checking a few things. I am getting current from both the green and brown wire going into the field coil, so the issue seems to be that it is not grounding? When I pulled the connector off while running and powered the green wire from the field coil directly to the battery and grounded the black one it started to charge, not great but it was noticeable. What Im trying to figure out now is why they both have 12v. I assume one of them needs to be grounded but the more I get into this the more confused im becoming.

To answer your question yes all this was done with the bike running. I checked the brown wire and green wire at the regualtor and both are supplying volts. For any of yall that have been through all this please help me wrap my brain around this I feel like im getting close.
 
13V is about what I get too, it should get even higher when you are riding, so I would just wire it up as it is. The regulator you have is the wrong type for your system, but you can still use it if you ground the other terminal of the field coil. I would also pull out the brown from the connector on the wiring harness and insulate it with either electrical tape or shrink-wrap. Otherwise, you can just get the switched-ground type regulator the Drewcifer mentioned in his posts.
 
Tried that, it will only charge with it hooked up to 12v constant and the plug disconnected. As soon as I plug the regulator in it won't work. Went and got an r296 from oreilys and its not doing anything either.

Update: I have a charge! Had to switch the wires around on the new reg and its working now. so far the highest I have gotten it to go was around 12.9. However the battery isnt in the best shape so I will try a new one but my headlight no longer dims to a candle and at least it charges. Now onto the clutch issue...Haha
 
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Sounds like you have a dead/dying battery with low amps. That will not be worth the trouble you spend fixing it. Trust me, a new battery for 50 bucks is well worth it.
 
Yup, it was given to me already in pretty rough shape. Im sure riding it for months with no charging system didn't help any :doh:. What a difference, the bike ran like a raped ape. I want to thank all you guys for the help so far, couldn't have done alot of this without yall.
 
There's a small gel battery on ebay from Battery Geek that's a good product and is listed for 750-900cc bikes with electric start.I got one and it works well,and is smaller in all dimensions than stock.I think it was about $39.00 with shipping. lha
 
Well I've been riding the bike around for a bit now and it has done really well up until now. It seems to be having a few issues that sorta popped up.

Im getting a bucking whenever I apply slight throttle, goes away as soon as you open it up a bit more. I noticed a popping on decel today too that seems to be new, not terribly bad as I can only hear it pop maybe once or twice when Im coming up to a stop. I didn't re-sync the carbs after I got the charging system working since it seemed to still run the same, would I still need to? From the plugs the bike has been running rich.

My starter is making like a sparking sound occasionally instead of starting. It seems to be pretty random when it does it.
 
Well I've been riding the bike around for a bit now and it has done really well up until now. It seems to be having a few issues that sorta popped up.

Im getting a bucking whenever I apply slight throttle, goes away as soon as you open it up a bit more. I noticed a popping on decel today too that seems to be new, not terribly bad as I can only hear it pop maybe once or twice when Im coming up to a stop. I didn't re-sync the carbs after I got the charging system working since it seemed to still run the same, would I still need to? From the plugs the bike has been running rich.

My starter is making like a sparking sound occasionally instead of starting. It seems to be pretty random when it does it.

richen your fuel mix up a bit
 
Ya I was planning on adjusting the mixture a bit. I was more curious than anything as to why it would start running leaner all of a sudden.

As for the starter issue has anyone ever experienced this, is that a sign of failure? I don't want to keep using it if it could cause any problems.
 
Well if you have been running with a weak spark, a rich mixture would not burn properly. You may have compensated previously by leaning out the mixture to get a more complete burn. Strengthening the spark gave your engine the ability to combust the AF mixture at the right temperature. With the same mixture as before (weak spark, lean mixture) but a stronger spark, you wind up with a lean, too hot, burn.
 
Your starter clutch might be getting bad. Or the starter itself might have a short in it.
 
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