Charging Systems — More efficient, and a cooler engine.

A clever update and worth sharing.

Firstly, I can't take the credit for this because I read about it on GS Resources forum, but here's a cracking little modification you can make to your bikes that are running the old style shunt regulators. But first a bit of history.

Back in the day when alternators were beginning to pop up on bikes in the late fifties/early sixties, voltage regulation was pretty basic, or non-existent. There was a finned rectifier to turn the Alternating Current (AC) into the Direct Current (DC), needed to charge the battery, but otherwise it was very basic. Extra alternator coils were switched into use by the light switch as more power was needed. Not ideal but it worked... in a fashion.

Then came the Zener Diode.
This amazing little device transformed charging systems by regulating how much voltage was allowed to get back to the battery. Sitting in some sort of aluminium heatsink, it would allow current to flow freely until it reached a certain voltage. Then, any excess current would be dumped to earth and the heatsink would dissipate the energy into the surrounding area as heat energy. 

Regulator/Rectifiers.
Everything at this point was kept separate, the rectifier did its job and the zener the same. 
The next step was to place them into the same housing, sealed with some sort of rubbery compound and forgotten about until you found your battery fizzing away one day with a dose of 18v going through it at high RPM.
If you ever read a write up in Used Bike Guide years ago, you'd be familiar with stories of how the standard regulator had blown on certain bikes, and how you could use one from, say, a Honda. Anyone riding bikes of the seventies and eighties would know only too well about these issues. So you just bought another regulator, probably a new battery too, and you were good for another few years.

  
Downfalls with the Zener Diode or Shunt Regulator.
What I hadn't realised with this basic type of regulation is that the stator windings start to run really hot when the excess power is dumped. They're always trying to charge the battery and the faster the engine turns, the more power is produced. But it all gets dumped and turned to heat to prevent the battery being boiled dry. 
This, in turn, will make your engine run hotter and eventually the components in the alternator burn out. You read that right. The engine itself will run hotter, along with the oil, because the stator is working harder as excess power is dumped via that too. Not so bad with a water-cooled engine, but a pain for an air-cooled lump, especially in hot climates.

A stator and rotor run in ideal conditions — an engine running cool, with clean oil — should last for years, if not for the life of the bike. After all, they're only fixed windings with a magnetic rotor running on the inside or outside. The problems arise when they get hot, expand and begin to rub on the rotor/flywheel. Once this happens it's pretty much all over.

Mosfet/Series Type Regulator.
The regulator pictured at the top of the page comes from a Polaris ATV, and it's a bit cleverer than your generic version. Rather than dump all excess current as the engine spins faster, it cuts or switches the power, rather like a duty cycle. Now the stator gets a much easier life because it's not trying to increase output with engine revs, and should last much longer. If more power is needed, because of lights, heated grips etc., it is switched back in as normal.

Check out the various forums and you'll find riders updating modern Aprilias, Triumphs, Suzukis and more to this style regulator and fixing their charging systems for good. Permanent magnet alternators always worked harder the higher the RPM, but not anymore.

What am I looking for?
Either the genuine Shindengen item, or a replacement for their SH775. It's now being fitted to no end of vehicles, including the Polaris ATV's, and aftermarket versions are reasonably priced and easy to find. The three wires from your three-phase alternator go into the grey coloured plug (in any order), and the terminal in the black multiplug, closest to the grey one, is the positive outlet (the other being negative).

I had already bought a standard shunt regulator for the GSX, but needed another for the GS550. I've decided to put the basic one on the GS, and try the series version on the cafe racer. Once everything is completed, I might try a swap around to measure the difference in engine temperature.

For a better explanation than I could ever give, check out Posplayr at GS Resources forum where you will get the ultimate guide to checking and diagnosing your charging system.