Charging System Faults
by Dan 'Shing' Shingler

Here's the deal. Your 86/87 VFR has one relatively weak point in terms of reliability. It may burn out it's regulator/rectifier unit by overheating it with too much current. This is most likely to happen when you've been charging the hell out of your system by running high RPMs through your stator (the thing with all the wires wound on it in your alternator) and creating more electricity than you need. Your regulator, bless it's hot heart, is actually burning off the excess electricity in an effort to protect everything else. For awhile anyway. When it fails, you could go and get a new Honda regulator. But since you're the kind of person who wants to own a 14-year-old bike, that's obviously not for you. You'll want to attack the problem by redesigning the bike in some way, instead. That's good, because putting another identical regulator into the same set of circumstances would only yield you the same results eventually. Duh.

Here's what's going on in your bike's electrical system and a couple of ways to fix it: Your stator is putting out a pretty decent amount of AC current. It's actually putting out more than you need a lot of the time. That current goes to your rectifier/regulator, which is one unit located conveniently under your seat. In this unit, the rectifier converts the power from AC to DC (who, ROCK, btw). Then the DC power goes from the rectifier/regulator to the rest of your electrical system. As long as the electrical system is using the same amount of power, or less, than what's being generated by your stator, the regulator waits patiently inside that magic little box. The system then runs off of your stator, or, if there's not enough juice there, from the stator and the battery at the same time. When the stator generates more power than your electrical system needs, the regulator soaks up the excess amount, leaving your system with just the right amount of electricity. In doing this, the regulator itself heats up -- it's sort of a little electric heater turning DC power into BTUs as inefficiently as it possibly can. As you can guess by the fact that your rear is all sweaty, there's not a lot of ventilation under your seat to help it cool off. One day, it may finally give out and generate more heat than it can survive. Like Romeo and Juliet, it doesn't die alone, though, because it's in love with and cohabitating with the rectifier. When it goes, the dismayed rectifier, in all probability, will kill itself as well. Then you're screwed, or about to be. Now the excess power that was being soaked up by your regulator is going to your other electrical components, which have no choice but to use it to generate heat of their own. Soon, the stator will succumb as well. Then you no go no more.

So, what should you do? There are two ways to attack the problem. The cheapest is to buy a tougher regulator/rectifier unit. That may work forever, who knows, besides you now need one anyway and why buy the same model that just blew out. A tougher unit probably will work at least longer than your Honda OEM unit, especially if it's not subjected to a lot of long periods of high RPMs with a fully charged battery. If you really want to get to the root of the matter, though, you can replace your stator. You can get one where the wires are wound differently and the power output is not as great, but still enough to keep your battery well charged so long as you're not running a bunch of electric vests, intercoms and other power hungry devices off your bike. Or, you could get both the new stator and the tougher regulator/rectifier and take off for Alaska. We know of at least one company that makes units to accomplish one or either of these tasks. It's here:

To find out if you need to do any of this (assuming you didn't just pull over because there was smoke coming out from under your seat) take your seat off, remove your left side cover, undo your fuel pump mounting bolt and unplug the coupler between the stator and the reg/rectifier. With an ohm meter, measure the resistance between the the coupler terminals, and check for continuity between each terminal and a grounded point. If the resistance between the couplers is not within a range of 0.2 and 0.5 ohms, or there IS continuity between either terminal and ground, your unit is bad. Bad regulator, Bad!

Replacing it is pretty straightforward, as it's right there in front of you, so we won't go into that here. If you want to replace the stator, you have to go to Grants, N.M. and see a guy named Dave, who provided us with most of the wisdom you are reading here. Just kiddin', here's what you do: Take off your lower fairings and put something under your alternator cover to catch the oil that's about to fall out. (This would not be a bad time to change your oil if you're even close to needing it, in which case you should drain the oil first. But put the container under the alternator cover anyway, there'll probably still be some coming from there). Take off your alternator cover. Hold the flywheel while removing the flywheel bolt. If you don't have a flywheel holder or an impact wrench, good luck, it can be done, we're sure. Using a rotor puller, remove the flywheel. Take the woodruff key out of the crankshaft (never thought you were gonna even SEE your crankshaft when you bought this bike, huh?!). Disconnect your alternator from the coupler that connects it to the regulator/rectifiier wires (we talked about that earlier, 'member?). Disconnect the alternator wire from the clamps and remove the wire clamp attaching bolt and wire grommet from the crankcase. Remove the four mounting bolts on the front of the stator and pull out the stator. Now put some loctite on the stator mounting bolts and install the new stator and wire clamp with the attaching bolt. Route the alternator wire back where it was, secure it with the clamp and connect the wire to the coupler coming from the reg/rec wires. Put the woodruff key back in the crankshaft slot and align it with the slot in the flywheel when you put the flywheel back on. Torque the flywheel bolt to between 8 and 10 kg-m or 58 -72 ft-lb. Put a new gasket on the alternator cover, slap it on and ride away.

Wait -- your oil!! Good gawd -- we gotta tell you everything?! Fill the damn crankcase back up with oil, THEN ride away.

Disclaimer: This information has been been reviewed and, where possible, verified. We are not, however, responsible for any mistakes or omissions that have slipped past us. When in doubt, seek official verification.