Permanent Magnet Alternator Mod


XS400 Addict
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Pittsburgh, PA
I just finished upgrading my bike to a pma charging system, and since it went so well I figured I'd write up a guide for it to give back a little to the community. The fragmentary information from the thread we have on this forum isn't really of much help. This isn't a difficult project, but it is a project. If you have this guide and the right tools, it could be an evening of work. Of course, I had neither this guide nor the right tools, so it took me a week's work and a whole lot of dremel bits. It's not difficult though and I highly advise this as an off season project.

My volt readings turn up 14.45 volts from idle all the way up the revs, and up to 10 volts just from a solid kick.

Here's a parts list and my total cost, minus shipping:

ZL600 Stator and Flywheel ---------- $25
Banshee Stator Plate ------------------ $15
3 Phase Regulator/Rectifier --------- $13
XS400 Gasket 1L9-15461-00-00 --- $12
M16x1.5 Bolt ------------------------------ $5

Home Depot:
Sheet of Steel ----------------------------- $8
Wires ----------------------------------------- $15
Dremel Bits -------------------------------- $10
M6 Nuts ------------------------------------- $2

Total: $105

The power tools I used were a dremel, a drill, and a weak soldering iron. I don't advise it.....

The project is pretty cheap for the amount of return you get. I did get a steal on the stator & flywheel though, you may spend more. I highly advise getting the ZL600 Flywheel, or any other flywheels that may be identical to it. I purchased a banshee flywheel I planned to use, the ZL flywheel just happened to come with the stator I bought, but the fit of the banshee one was really poor. It barely sat on the crankshaft and stuck out so much that it barely reached the stator, and the cover would not fit without modification. The ZL600 flywheel on the other hand was a perfect fit. No modification needed, just bolt on and admire how perfectly it fit in the casing and over the stator. At first I was concerned because the flywheel seemed to be about half the weight of the stock one, but have no fear. Since the weight is distributed farther from the center of rotation, it actually carries the same or more inertia than the stock one. It feels to me as though it has more power coming off idle.

Step 1: Disassembly

I didn't take any pictures for this process, but it's pretty self explanatory.
Firstly, drain a pint or two of oil and put the bike on the center stand so that oil doesn't pour out of the bike. Put something down anyway, because some oil will drip.
Unscrew the 4 screws holding the "Yamaha" cover, and remove that. Under this, you will see three more screws. Unscrew these and set them aside for later, we will be using them. Then unscrew the casing bolts and remove the crankshaft cover. Unscrew the three screws holding the outer stator coil in the crankshaft cover and set those with the other screws, because we will be using those also.
Now turn the cover over and knock the coils out through the holes. You will notice that coming out of one of the wire bundles are two wires that attach to funky spots on the engine. These are the neutral and oil pressure indicator lights. Follow the wires to the plug up by the front of the battery box. Pull from the plug the four leads that are used for the connection of these two wires and then cut the plug. Reconnect these wires and shrink-wrap/tape.
The bolt holding the flywheel/rotor is probably on there pretty good. What you want to do is put the bike in 6th gear and lock up the rear wheel with a bar. Then just lean into it and get that bolt free. To take off the rotor, you are going to need the proper bolt to thread into it and against the crank shaft; it won't just fall off for you. It's an M16x1.5. With the wheel locked up like above, but in the opposite direction, thread the bolt in till it seats. Then put a wrench to it and hit the wrench with a mallet till the rotor falls off.
Remove with it the starter motor gears and chain. Pull the starter motor too, because you wont be using that anymore. Put the clutch-side gear with those bolts you saved, you'll be using that too.
Then use a 1 3/4 inch expansion plug to plug the hole where the starter motor was. It's got to be short enough to sit below the gasket seat, otherwise you will have to make a hole in the mounting plate to accommodate it.
Now that you've got a bare crankshaft, you should look something like this:

Step 2: Fabrication

Now's where things get fun. Unfortunately, if you have access to a CNC or some such metal working machine, you'll miss out on all the good times. If not, scrape together your cutting/sanding disks and drill bits. We will be making a steel plate to sandwich between the engine casing and the crankshaft cover, onto which we will mount the stator.

The first thing we are going to do is prepare the stator mounting bracket. You will need to cut a little notch in the top where the stator sits to accommodate the wire-routing screw on the underside. Here it is circled in red:

Next, you need to cut off some material that will get in the way of the cover, as well as the feet on it, which will allow it to sit at the ideal height on the mounting plate. Here's what the final product should look like:

Go ahead and bolt your stator on, using the bolts I told you to set aside and some blue loctite. They are a perfect fit. Here's what it should look like (I used other bolts because I had them, and I used those bolts to mount the regulator):

Now we're are on to making the mounting plate. Here's the final product we are looking for:

If you have access to a CNC machine, this will be a 30 min job in CAD. If you are a cheap bastard and only have a dremel and too much time, you can follow how I made it.
What I did was cut a rough shape with a dremel and then laid the crank shaft cover over it. I then marked two holes to drill where the bolt holes provided enough space. I drilled these out and bolted the piece onto the cover, using random bolts from dissassembly, then flipped it and did my best to drill the other holes perfectly centered from the other side.
Then I used the long bolts from the final drive cover to bolt the piece to the engine casing, up against the crankshaft. I then marked a hole to drill for the crank shaft and proceeded to drill and dremel that out. Now you can try to screw the piece onto the engine. If you're like me and your largest drill bit you have barely accommodates the screws, you will have to wiggle the holes a little because the threads in the casing don't line up perfectly with the holes on the cover.
Now try to drill out the holes for the aligning studs. As you can see in the picture, on mine I only drilled out the hole for one. That is because my bolt holes are so tight that they align the piece, and the hole drilled around the tip of the expansion plug holds up the other side. I'd advise you to not do it this way and just make sure you drill the holes out perfectly.
Now to drill the holes for the stator mounting bracket. This part is important because it is essential that the stator is perfectly centered. There isn't alot of clearance and you don't want your flywheel rubbing on your stator. Luckily I came up with a trick to do this. Before you do this, put the stator and bracket into the flywheel and set the flywheel on the crankshaft, over your mounting bracket. Look at where the hole is in the cover for routing the wires and think up how you will manage to get the wires there without the flywheel touching them. I tucked them under the upright part of the bracket and looped them back. Now, outline the three legs of your mounting bracket in this position. Go pick up that starter gear I told you to put aside. Now try to slip it into the hole in the middle of the stator. Doesn't fit. Now look at where the parts meet. The rim of the stator sits right on the taper of the starter gear. Now go pick up the bolt that held the flywheel onto the crankshaft. Take the washer off it and put it inside the starter gear. Almost a perfect fit. So, what I did was wrap the washer in tape to make it a perfect fit in the starter gear, then make a cardboard washer to go around the bolt. Secure your mounting plate to the engine casing and slip the stator and bracket over the crankshaft. Put the washer into the starter gear and the cardboard washer over the bolt. Slip the blot through the starter gear and the washer, and seat the starter gear onto the stator. Then thread the bolt into the crankshaft until the starter gear perfectly aligns your stator onto the mounting plate. Orient the stator to the position you marked and mark drill holes using a dremel with a drill bit. Make sure these are placed so that the bolt will not to hit one of the ribs on the engine case. Again, precision is important. I suggest you mark them so that the plate cannot rotate so that the wire alignment doesn't change. Take the part off and drill the holes, constantly checking to make sure the bracket still lines up with your markings and the holes perfectly.
Now that that's done, cut some holes into the plate to allow some oil flow. Then just bolt the part to the cover and dremel the edges down flush. Congrats! You saved some money. Bandage your wounds and move on.
Step 3: Assembly

Get those other screws I told you to set aside and use them to mount your stator bracket to your mounting plate. Just put a nut on the other side with some blue loctite.

Then bolt the plate to your engine casing and put the flywheel on the crankshaft. Spin the flywheel and make sure you can't feel/hear it rubbing the stator. If you can, you are doomed. If not, heave a sigh of relief. You can also pull your spark plugs, lightly bolt the fly wheel on, plug in the regulator, and kick the thing over to check for voltage output. You should get several volts with a kick.

Now get your gaskets, the original one and the one you ordered, and trim the insides such that they fit around your bracket and the nuts.
The only thing left to do is button the thing up. I suggest that you assemble everything in the cover and then just bolt that onto the engine case. That way you can be sure about the wire placement and it is just more convenient. Put the alignment studs in the cover, place the first gasket, put the flywheel over the stator, place the stator mount, place the second gasket. Use a small screwdriver to make sure the wires are in place. It should look like this. You can see the flywheel suspended around the stator by magnetic force.


Now just set the assembly onto the engine case, the flywheel slipping over the crankshaft. Bolt the cover on and the flywheel down, using the same method as when you removed it.

Screw the cap on and you are good to go. Can hardly tell the plate is there. You can sand and polish it finely if you want, but I didn't care much for mine.

Now onto the final step, wiring.

Step 4: Wiring

This part is pretty easy. Firstly, you are going to need to find a good place to mount the regulator. These things can get alot hotter than the stock unit, and if allowed to do so will age rapidly, so you want a place with plenty of airflow. I put it under the headlight bucket where the horn was because I'm planning on upgrading to an air horn anyhow. Works like a charm. Don't try to mount it underneath the horn or you'll end up with a regulator-sized dent in your fender. Don't ask me how I know. The mounting plate is basically just a rectangle with 4 holes, easy work. Also, any 3-phase regulator will work, they are not device specific. Just make sure it has 3 similar colored wires and 2-4 wires for + and -. Mine had 7 total, three yellow, two red, and two green.

Now you are going to need to hook up some wires to connect the regulator to the stator coil and to the battery. You are going to want about 18ft of yellow wire and like 5 ft of slightly thick red and black wire. Cut your wire to the lengths you will need to attach three yellow wires from the regulator to the stator, 1 yellow wire from the stator to the front of the battery box, and the 2 power wires from the regulator to the back of the battery box, where the rectifier was plugged in. Start off on the regulator end, with the three yellow wires and the power wires. You can re-use the plugs from the old regulator, rectifier, and stator; just cut them off, pull the leads, and solder on the new wires. Solder on the appropriate plugs to attach to the new regulator/rectifier unit. If you have 6 wires or under and room in your headlight bucket, you might want to use the old rectifier plug for convenience. Otherwise, the old regulator plug works well for the 3 stator wires Based on the length of the wires coming out of the regulator, you will have to find a good place to route the wiring. I tucked the stator wire plug in the headlight bucket and the output plug under the tank. Here's what it looks like:

Now you need to fork one of the stator wires off to attach to the headlight relay to flip the switch and power the headlight when the engine turns over. The relay disconnects the trigger circuit after the headlight turns on, so this shouldn't affect your power output. I did this by using a four prong plug at the stator connection, three of the wires going to the regulator and one of the wires going to one of prongs on the plug the old stator used to be connected to. This plug should have 3 wires of the same color, probably a very faded yellow, and one of a different color, probably a very yellowed white. We need this to connect to the white wire. There's a picture below showing where the wire was on my plug. That connection was just temporary, you are going to want to take the plug off and at least wrap that up. On the other end of the stator plug I have this wire looped back and soldered onto one of the stator wires. Here's what that looks like.


If you look at the stock rectifier, the one with a 6 prong plug, you will see 5 wires coming out of it. One black, one red, and 3 yellow. This is where you will want to attach the + - output of your regulator. The red goes to the fuse box, then the starter solenoid, then the battery. The black goes to ground. You can get rid of the starter solenoid if you want to but I didn't do that. If you didn't already cut the plug, pull the leads for the black and red wires and solder the rectifier-side leads onto your output wires. Hook them up and shrink wrap. If you did cut the plug, just use leads from one of the other plugs. Get rid of the other wires how you see fit. I cut them to different lengths and shrink wrapped them, but I'm sure there's a better way:

Then just solder a plug to attach to your stator and your regulator should be all hooked up.

And that's a wrap! Congrats, you just upgraded your shitty stock charging system to a fancy pma charging system. Check your voltage and you are good to go.:thumbsup:
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Looks good but I have one question. Where are the timing marks on the rotor for setting the valves/ignition?
Thanks guys, glad to be of help. I actually neglected to make timing marks on the rotor. That's a no no, I know. The flywheel has no alignment key so any marks made would be rather useless if you ever removed the flywheel. What I will do though, after a couple weeks of running it to make sure everything checks out, is hook a light up to the points and use that indicator to make marks for my current timing. I will update the op when I do that. Anybody have a better idea?
I'm not sure about the sheet thickness actually. I'm pretty sure it's 16 gauge, but I just went for not to thin and not too thick
For the timing marks you can always find TDC by sticking screwdriver into the spark plug hole (as you rotate crankshaft the TDC is in the middle between the points when screwdriver stops going up and starts going down ), and to set ignition timing mark if you know how many degrees to set it to - draw a circle the size of flywheel on the paper , draw the sector of needed angle and you will see how far to make timing mark from TDC mark.
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Thanks for that bit of info Norman, and the suggestion NJ.

After hooking up my headlight I figured out that the headlight relay trigger was directly connected to the old alternator, so my headlight wouldn't work. This can just be triggered by any live wire so that the headlight will always be on when the ignition is on, or it can be hooked up to the regulator output with a diode so that it will only come on when the stator has generated power ie. the engine has been turned over. Might be able to hook it up straight to the stator output without a diode, I'll check that tomorrow. Will update the op when I'm done
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Ok, so I think I get it. The stock system had AC current from the alternator going through a diode to provide the relay with a trigger charge which closes the relay. The trigger circuit is then disconnected and 12V DC output from the battery is connected, powering the headlight. I think that using a live wire to trigger the relay might actually short the battery in the moment it takes to switch the relay. Nominally it seems to work fine, but I'd imagine that would affect battery health. If that's true, hooking it up to the regulator with a diode could similarly affect the regulator, but perhaps because the voltage is so low when the relay is triggered it wouldn't have any affect. That seems like the same principle with the stator output, because shorting high voltage AC current would mess you up just the same. Am I on the right track? My conclusion is to just do as I planned and hook it up to the regulator with a diode preventing back current from the battery.

EDIT: After reading more, hooking it up to the regulator with a diode isn't a good idea because that would cause a .7V drop in the whole system. Seems like the best option is to fork one of the stator wires to the relay trigger with a diode so that the rectified stator output will trigger the relay, then the circuit would disconnect allowing all the AC current to flow to the regulator.
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Oh and looking through that thread gave me a greater respect for the stock system. Its actually pretty cool, much more efficient than the PMA system. Too bad they couldn't engineer a similar system to have consistent output.
I wanted to get to that depth of knowledge on my own, but those two owners brought more info to the knowledge base, and I am glad it made it to 4 pages. I still hold to my thought that white wire is just supporting added power to the headlight, which I kinda got, that was understood from this thread, (loosely understood). You can always jump the line, and get the headlight to work. but if the bike isn't running, it is more important to worry about headlight, after its is running, than otherwise. chances are, once it is running, the headlight will be fine. (unless someone starts hacking at the wires, like in scorpios case, and others, just cause they didn't understand the principals of that system.
The bike is running arfstrom, and the headlight works just fine, I'm just trying to find a reliable way to hook up the relay so that it works like it did on the stock system. I'm pretty sure I've got it figured out, just need to get me a diode.
The guy in that thread, went and got him one. Its listed about page 3, He stated the brand, type. Then the other guy, showed off his, lack of a better word, Doo-dad. something with a ton of resistors.