Well, why don't we start with a 'bang', and show you the ugly side of what we're talking about...
In case you're not familiar with these critters, it's called a stator. And this one is a particularly well-fried example, extracted from my very own 'Flying Banana' in Jan 2005.
"Now that is indeed unfortunate," I hear you think, "but why should it bother me?"
It should bother you because if you have a GS or GSX Suzuki, it is only a matter of time until you are staring at one of these cooked lumps of coiled wire. In fact, the last time I took a stator in for a rewind, the motorcycle lekky bloke said with a smile, "If it wasn't for Suzuki we wouldn't have a business!" Which might be true, but his thinly-veiled glee did nothing for my hip-pocket misery.
So yes, this is frustrating, expensive, and trust me hard to come to terms with. So much so, that it is a recognised disease: 'stator denial'. Which is when the GS or GSX owner tries every other fix in the book to sort out why his battery is continually going flat, instead of seriously considering the one possibility he desperately hopes it isn't, viz. a fried stator and (almost always) a cooked reg/rect. unit into the bargain as well.
What to do? Well, first let's cover a few basics. The stator resides under the left-hand engine cover of every GS/GSX Suzuki. Put simply, it's half of an alternator; in the GS/GSX Suzukis, it is bolted to the inside of the engine cover, while the rotor which contains a set of magnets is mounted on the end of the crankshaft and spins around the stator (see pic below), thus generating current and doing useful things like charging your battery, powering lights, ignition, blinkers and all the good gear.
Now, looking at the rather toasted example above, notice: (i) the windings which have cooked themselves into an almost welded state, and (ii) how there is actually a pattern of cooking discernible as you count around the windings in multiples of 3 that's because these are three-phase alternators and one phase has copped a bigger punishment than the other two. The burning question (look Mummy! a pun!) is, What causes your stator to become so nicely roasted? To answer this question we will have to engage in a not-too-fanciful reconstruction of ancient Suzuki history...
Once upon a time at Suzuki, boys and girls, there was an electrical technician who had what he thought was a brilliant idea. A three-phase alternator is a wonderful apparatus, mused our tekkie, but there are times when the full three phase delivery is a bit of overkill. So, why not set up the system so that only 2 phases are used when the headlight is off, but when you turn the lights on the 3rd phase jumps into action?
Now this is why if you look at the original wiring diagram of just about every GS/GSX Suzuki, you will see that two of the wires coming from the alternator enter the regulator/ rectifier unit. But the third wire representing one of the phases heads off to the headlight switch on the right handlebar switchgear, and then back to the regulator rectifier. So, the third phase was only delivered to the reg./rect. when the headlights were switched on...
Well it was all OK in theory, I suppose, but it had an unfortunate side-effect. Ask yourself this: What happens to the juice of the third phase, when it can't go anywhere? The answer is, it generates heat enough heat to start cooking the windings, so that after a few years you notice that your charging system is struggling to deliver enough juice to your over-taxed battery.
Oh dear. Now I'm no electrical wizard (as the more technical among you may have picked up from my ramblings thus far) but as I understand it, this state of affairs had other undesirable results, namely the cooking of the diodes in the reg./rect. in due course, and then causing short battery-life as the poor thing tried to cope with all that un-rectified electricity being dropped into its lead-plated lap.
So where does this leave us? It means that to put things right, it is not enough to get a rewound stator and a new reg./rect. unit which are both rather expensive items in their own right. You must fix the cause that is, that wretched wiring arrangement conceived by our nameless Suzuki tekkie (and if he has any sense he will take care to keep his identity concealed!).
Fortunately this is simple to do you don't even need a soldering iron! (Although soldered joints are always best because you eliminate the possibility for a poor connection and therefore high resistance and heat at that point.) Where the offending wire heads off up the wiring loom from adjacent to the reg./rect. and onwards to the right handlebar switchgear, there is a bullet-style connector. And likewise where it returns back along the loom and exits near the reg./rect., there is another bullet-style connector. Simply pop apart each connector, and plug the third phase coming from the alternator into the wire that goes straight into the reg./rect. unit and voila, you have it sorted. And the remaining wires that are now redundant? Just coil them up out of the way and forget about them.
Now I could ramble on about what to do next and how to ensure that the other aspects of the electrical system are in good shape but why bother? The good news is that if you go to the GSResources website, you will find what are called 'The Stator Papers'. Here you will find all the theory, trouble-shooting diagrams, and advice you will need.
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If you're after a replacement stator, or a new reg/rect. unit, Electrex stuff is well-priced and they'll mail it right to your doorstep.
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And, one more thing. Given that Suzuki electrics will go belly-up at several-yearly intervals anyway, you might like to hook up a small but effective LED voltmeter somewhere around your instrument console. For a great circuit diagram and clear directions for constructing a 'minimalist' unit, go to Jörg's website, here.
If you're in Australia, another option is to go to Dick Smith Electronics and buy their LED voltmeter kit (Web ID. K4205) off the shelf. It only costs about $10, and if an electrical ignoramus like me can cobble it together so that it works a treat, then surely you can, too. I ended up housing the small PCB board and the electrical gizzards in a small aluminium box I made up, and then filled it up with epoxy resin ('Araldite') so that the unit is fully dust-proof, water-proof and vibration-proof. It now resides on the side of the instrument cluster courtesy of some double-sided adhesive tape, ready to tell me when the battery or the charging system is starting to drop off the perch. Not that I really want it to die in a hurry.
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As you know, the wiring diagram in most Suzuki manuals is an eyeball-twisting pain. Lines crossing lines, dots, dashes, funky little numbers and obscure codes... you need a lot of patience to navigate the blasted thing. Why Suzuki never decided to safeguard our sanity and churn out a colour-coded version of the diagram...
But never fear! Hus has come to our rescue and produced a colour-coded version of the diagram! The bloke must have spent hours doing us this kind service, so if you get the chance please send him a line of thanks, he deserves it.
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