All information in this document is believed to be correct, and is presented primarily for educational purposes; it is not intended to be a service manual. Use of the information is at your own risk; if you are unsure of any of the concepts discussed here or are unwilling to assume that risk, contact qualified service personnel.
On any modern vehicle, there are parts which consume electricity; that electricity has to come from somewhere, which is the charging circuitry. In the old days they used to used magnetos for ignition (still found on lawn tools) and before that make-or-break (too hard to explain. i've seen it on one of Dave LeClercq's old old donkey engines, basically there isn't a spark plug, there's a switch inside the cylinder head where the spark plug would be.. when it opens it makes a spark). A Rectifier-Regulator is a standard part of the electrical charging circuitry on most recent (whatever that means) motorcycles. It differs from the usual automotive charging circuit primarily by its use of a shunt regulator, which "soaks up" excess electricity instead of preventing its formation in the first place.
THE
ALTERNATOR consists of two electrical
coils. The stationary (yellow) one is used as an electromagnet,
and is called the field coil. The rotating (blue)
one is the one that gives us power. It does this because when
you move a coil inside of a magnetic field, it induces an electrical
current. Because the coil rotates in a magnetic field, the current
flips back and forth, which is called alternating current.
THE AUTOMOTIVE CHARGING CIRCUIT uses a regulator which controls the output of the alternator by varying the strength of the magnetic field in which the stator coil rotates. The rectifier is often part of the alternator assembly. The regulator is typically a separate small box. Regulators can be mechanical (another electromagnet pulls apart the contacts which send electricity to the field coil when the system is fully charged) or solid state; the ignition switch typically takes the regulator out of the circuit since the sensing circuitry draws a small amount of power and would eventually drain the battery down.
THE MOTORCYCLE CHARGING CIRCUIT uses a shunt regulator. The magnetic field in the alternator is generated by means of permanent magnets. The rectifier and regulator are usually combined into the same assembly. The shunt regulator works by bleeding off the electricity from the fully-charged circuit. This means that when the battery is fully charged, the shunt regulator makes a lot of heat! That's why motorcycle rectifier-regulators have cooling fins.
These things do just fail from time to time. However, before going to the time and bother and expense of replacing one, it is prudent to consider if there are contributory factors. You should conduct a postmorten electrical system check and verify that all components are in good working order. You should perform some basic postmortem checks on the RR itself, and attempt to determine what has failed, internally. The diagnostics required to do that are beyond the scope of this document. I recommend you check out Electrex USA, both for their troubleshooting guide and also as a source of replacement parts (when I had to replace mine, it was late on a Friday; nobody answered the phone to check pricing or availability, so I started calling dealers and one of them actually had one in stock so I bought it even though I probably paid more than I needed to).
"It's dead, Jim!" -- famous line uttered several times by McCoy in the original Star Trek television show
Total failure does not usually mean that every part inside the unit died at the same time. All of the parts share a common ground or hot connection; if the unit tests out totally dead, then this internal "bus" connection probably failed. This is typically due to either a manufacturing defect or else excessive heating and cooling. A failed connection can cause any of the observed failure modes, so keep that in mind: just because the device doesn't test out totally dead, doesn't mean that it wasn't defective or simply overheated one too many times.
If this happened, your battery probably stopped holding a charge, the lights got dim, and you had to park it. The circuit diagram above is simplified, and shows a half-wave rectifier; in practice, full-wave rectifiers are typically used. In such cases, if a single diode fails you get half of the charging output from the RR.
If the diodes (rectifier) tests out bad but the regulator (zener) tests out good, be on the lookout for a short or bad connection to the alternator stator coils. A sloppy connection can cause some serious voltage spikes, which can destroy diodes. Check also for a bad battery connection; thankfully, the integrated shunt regulator should provide some protection against this (unlike the automotive circuit), but again it could cause some serious overvoltages. A shorted battery could cause the diodes to draw too much current and burn out as well. A reversed battery could burn out the diodes.
If this happened, your headlight probably got really bright... until it burned out. Your battery probably boiled dry, too.
If the zener (regulator) burned out, check your battery connections! Also, make sure that all of your running lights are working; remember, the regulator bleeds off excess power, and generates a lot of heat doing so. If all of the lights aren't working, that's more heat for the regulator to get rid of. Also, you didn't jump-start your bike from a car with the motor running, did you? Bad idea!
There is anecdotal evidence that a bad battery can stress the RR. As noted, if your running lights aren't working, that makes the shunt regulator work harder.
So, now we get to what this page is all about! To replace the RR, you will have to take your VX apart.
Easy peasy! It's held on by the two allen head screws.
The side bodywork comes off pretty easily. First, remember to disconnect the taillight. Then, remove the two screws (one on each side). Finally, pull gently to release the press-fit nubs (two on each side).
To remove the gas tank, you first need to remove the two screws at the rear (see gas tank mounts in photo in previous section). Now, you need to lift up carefully, so you can disconnect the hoses which connect to the tank. There are two hoses going to the fuelcock, and two vent hoses. If you have a bike with the California carbon (emissions) cannister, these hoses are not interchangeable! The Aurora Suzuki Home for Clowns in Seattle Washington got this wrong three times in a row.. and botched the incidental repairs on times 3 & 4.. lying sacks of garbage... do not take your bike to these fools!
Once you get the hoses disconnected, you can pull backwards slightly on the tank to release it from the bracket at the front, pictured in the first two photos below (that blue thing in the second photo is a screwdriver holding up the tank).
You should perform some checks to verify that the RR is indeed the problem, and that it is the only problem. The types of tests and the specific steps to follow are beyond the scope of this document. The Electrex USA web site previously cited has a generic troubleshooting guide which can be downloaded. You will need a voltmeter and some jumper wires to perform the checks.
Note the close proximity of the wires and the fuel hoses in the pictures in this section and the previous one. Furthermore, be aware that an alternator in an open circuit can generate sufficiently high pulse voltages to cause sparking and a fire, as well as posing at least a slight risk of electrocution. If you've got one, having a fire extinguisher at hand is probably a prudent precaution.
Removing and replacing the RR is the most difficult part of the entire operation. The thing is mounted on a metal plate in behind the engine and underneath the exhaust crossover pipe. If you have a California carbon cannister, it will be directly in the way. Loosening the exhaust system will gain you a slight amount of additional clearance. The wiring harness snakes over the right side of the bike. The RR itself is held on by two phillips head screws.
Be sure your fuel tank hoses and electrical connections are good, and avoid pinching anything.
As you can see below, the replacement RR has one less wire (the orange one) than the original! What does this orange wire do?
Turns out it is a sense wire. So, what's in the RR is not just a large honkin' zener diode, but an actual shunt circuit. The sense wire connects (more) directly to the battery, and doesn't carry any appreciable current; therefore it theoretically gives a better reading of the voltage at the battery. If your electrical connections are sound, this supposedly doesn't matter.
Etz used the Electrex regulator.