The VFR R/R failure on the pre-2000 VFRs is legendary among VFR owners. It is probably the only real design flaw in the VFR. Many VFR R/R failures have occurred around 20,000 to 25,000 miles. But others have been as quick as a few thousand miles, and other owners have never had the problem. My VF1000R lost its RR at 24,000 miles, the VFR at 60,000 miles. Electrex makes an aftermarket unit, but it didn't seem any more reliable than the OEM unit, and some had worse luck with it. Even so, see their website for a good charging diagnostic procedure.
There are different theories about the cause of the failure of the R/R , though there is some consensus that heat is the main culprit. On the VFR, the R/R is bolted to the subframe under that tailpiece, close to a pretty hot engine, with minimal airflow, and without any cooling fins. Personally, everything I've experienced with R/R failure is consistent with the heat-death theory -- and Honda finally fixed the problem on the newer model VFRs by adding a finned heat sink to the R/R. Bingo! You may be able to forestall an R/R failure by adding cooling to the R/R. People have added CPU fans and heat sinks. Steve Donaldson came up with a cheap, easy, and inexpensive fix by using heater hose run from the front of his VFR back to the R/R to provide cooling air.
Poor grounding connections can also be a "cause" by preventing the R/R from doing its thing, which will 'cook' the unit. Clean those ground connections!
R/R failures seem to occur in one of two failure modes. I've experienced them both. Both can occur as intermittent failures, so it can be tough to catch it until things are really bad.
Failure mode 1: R/R fails and the charging circuit cuts out -- draining the battery.
Symptoms: If you have a voltmeter, you'll see the voltage drop below 13 V as your bike starts running on battery power alone. If you don't have a voltmeter installed, your first symptom may be when the bike fails to start one day. If this happens to you, DON'T ASSUME your battery is bad! Check the voltage when you get the bike running again.
If the bike is running, you may first see symptoms such as dim headlights and failing electrics (e.g. speedometer and tachometer fluctuations. Note that if only the tach is fluctuating, the more likely cause is a worn sprocket nut turning the tachometer cable -- an easy and cheap fix compared to the electrics).
In this failure mode, pretty soon the battery will die and your bike will too. Trust me, you can only get so much further with push-starts.
Failure mode 2: the R/R fails to regulate the voltage, and over-charges the battery.
Symptoms: If you have a voltmeter, you'll see the voltage go way up at any engine speed above 3000 rpm. Voltages such as 17-19 volts are possible and not a good thing. Your headlights may blow out, with the filaments burned out by the high voltage. Pretty soon your battery will be cooked, and your stator will possibly be damaged ($$$$).
If you have a voltmeter and you suddenly see the voltage jump to 17-18 volts, I suggest continuing to ride a couple of minutes while monitoring the voltage. If it doesn't go back to 14 or so volts, shut the bike down, wait a minute, and then restart it. The R/R may kick in again and work normally. If it doesn't, leave the bike off for a while to let the R/R cools down and then try again. Both these tricks worked for me.
If your R/R does fail, don't just replace it. Be sure to also check the condition of the battery, the stator, and the connectors. Check for discolored, burned connector at the R/R and replace as necessary. Clean and tighten all electrical connections, especially the grounding points on the frame. Also be sure to use dielectric grease on all electrical connections. Check the stator and R/R using the procedures in the owner's manual (you have one, don't you?) or the Electrex website.
If your R/R fails, be sure to get the new version to replace it! See a comparison of the new and old version. If you have the old version, I think it makes sense to order a new one as spare. It's not cheap, costing about $130 - $140. But if you don't have a spare, you risk getting stranded and losing a days riding -- and maybe paying the price of a tow, meals, and a motel room. It happened to me -- I've lost two R/Rs, one on my '85 VF1000R and the other on my '94 VFR, and both were while I was on extended trips. Fortunately, I had installed a voltmeter and so I saw the second failure happening and got a spare R/R overnighted to my next-days destination, thereby saving the trip.
For more information, see the FAQ at the Texas VFR Garage or the check the archives of the VFR Mailing List . Search the archives, and you'll get more hits than you care to read about this problem!
(c) Marc Brinker 2005.