regulator testing
Think of your regulator, as your battery's bouncer. Without it, anything can get in!
It happened to me. I was coming home from work one day, putting through town, and all of the sudden, it felt like someone pulled the sparkplug on one of my cylinders. I tried to twist the throttle to keep it alive, and the bike gave a half hearted lunge, but slowly started sputtering to a stop. With the clutch pulled in, I coasted to a stop in a parking lot.
After a short charge from a car battery, (with the car turned OFF), I was able to start the bike again. But I had to keep it around 4K rpms, otherwise I'd get the sputter that I didnt have enough juice to keep powering the sparkplugs. I pulled the headlight fuse, in an attempt to save energy. What happened? Well, I later found out that my regulator died. A little background.
Bikes have a alternator (stator), which spins at the speed of the crankshaft. At idle, the alternator should put out enough voltage, to "break-even". This meaning that it creates enough electricity that the bike does not have to draw from the battery. Above idle, the voltage the alternator will put out is exponential with the speed of the engine. On top of that, the type of current coming from the alternator, is Alternating Current (AC). So now we have a problem. Your battery runs off Direct Current (DC), and really shouldnt get anything more than 15 Volts, otherwise it'll start boiling, blowing fuses, or other not fun stuff.
This is where the regulator/rectifer comes in. It looks a bit like a computer chip. It has a couple wires coming out of it, some big cooling fans, and is located in the front, underneath the lower triple tree. This little device, takes the alternating current coming from the regulator, rectifies the situation by converting it into direct current. And if you thought it did enough, it also regulates the flow of electricity to the battery. Since the voltage goes up exponentially with the rotation of the engine, the regulator part, makes sure that voltage to the battery is enough to power the bike, AND charge the battery. Think of it as a bouncer at the door of your favorite club. He makes sure that enough people are going in, and coming out, so the place doesnt get over crowded. No bouncer, chaos.
So how can you test this? With a voltmeter. Pull up the tank on your Ducati, pull off the rubber booties from the battery terminals. First, test the battery (with the ignition off). When charged, the battery should put out around 12-14 Volts. Before troubleshooting electrical gremlins, always make sure your battery is charged. If you are getting less than 12 volts, then, you need to charge your battery. You can get a 12-volt battery charger from AutoZone for 13$. Even has mounts so you can bolt it to your bench.
Next, start up your bike. Here is the tricky part, you need to test the voltage put out, at various RPM ranges. I simply used the high-idle switch on my 900SSie to set the RPM's. You want to test the regulator from about 1,000RPM's all the way up to 5,000RPMS or so. So have your friend , or set your high idle until the bike is at around 1,000RPMS or so, and check the voltage readout on the battery terminals. Then change the RPM's in 1K increments until your at 5,000. Each reading should be no less than 12 volts, and no greater than 15.5 Volts. If your reading more than 15.5V, then your cooking your battery, and your regulator is busted. If your reading less than 12 volts, then its possible your regulator OR your alternator is busted. Check the connections, make sure everything is clean and loaded up with di-electric grease. In my case, I was reading about 11.52 volts at 2,000RPMS. I replaced the regulator, with an Electrux one from Ca-Cycleworks, and was promptly greeted with 13.3 V at 2,000RPM's.
