Over on the Gold Wing forums they have done quite a bit with grafting in automotive alternators external to the engine because the stock GW units just can't keep up with all the cruiser-type accessories that guys want to use, like heated riding suits, heated grips or gloves, tons of even LED lights, loud radios, hotter ignitions, etc. Of course, the GW flat four/six engines lend themselves nicely to tapping into the end of the crankshaft to drive an alternator. A good small car alternator puts out about 55 amps, and in the same size package they can be found up to about 100amps, using just one wire to feed the battery. Fortunately for us Voyager 1300 owners, our stock dual alternator systems give us 45 amps, which is plenty for most applications.
Although my previous Voyager had the stock system and it powered the bike and sidecar accessories just fine, I am looking at trying to figure out just how I could add an automotive one-wire 100amp system. My hack will have a blower for the heater system as well as a suspension ride-height electrical screw jack. I also plan to convert to all LED lights and adding maybe a few more, so that should actually drop some of the lighting needs. I will also be running an electrical water pump in place of the mechanical one, so that will add significantly to my electrical power needs.
I am asking why it is necessary to add more power on a simple street bike. The stock, single unit should be more than enough to power all of the lights and ignition. What am I missing?
The big reason I am asking is that a regulator looks at the battery voltage to know how much power to produce. The dual ZN1300 regulators are coordinated in some way to work together. Without a detailed description of how they do this, I would be VERY leery about tying a stock KZ system with an added-on ZN second alternator! MAYBE if you added the whole ZN system to a KZ's engine and made sure it spliced into the KZ's wiring harness exactly as it does the ZN's. Without that detailed explanation of how the two regulators do what they do, you are making some possibly dangerous assumptions.
Some of they guys over on the GW forum learned the hard way that you cannot add an external alternator and run it parallel with the stock system to charge the battery! Each one tries to keep a minimum voltage, and they jockey back and forth rapidly in that effort, eventually burning out both of them.
Unless someone here has actually done this modification, I would be hesitant to do it. Not enough electrical info to make critical decisions. And, like RickG says, better be really careful of farts! Your bike's name COULD become "The Ignitor!".