What's with all the Regulator/Rectifier talk? Is there something wrong?

Well, unfortunately, yes. Since the rest of the bike is perfect this issue gets a lot of attention. Honda made several errors in the design of the charging system, including connector sizing, circuit layout and cooling. When everything is new it works ok. When the various components get old it works less than ok. Since there's no way to know what's up till the bike won't run the electrical problems are uniquely apt to strand the rider.

The problems fall into three categories, which are ranked in order of believed (by this writer) significance.

1. The battery does not have a short, dedicated connection to the RR

2. The connectors between RR and bike harness are too small.

3. The RR gets very little little airflow in the pre '02 bikes.

Much has been made of faulty stators; this writer is skeptical. Items 1 and 2 are enough to account for most tales of woe. Physically it's very implausible that a short in a generator could lead to _increased_ performance. Unfortunately, stators do fail anyway: Both the VFR and my SV650S have required replacements. It's just that the failures aren't likely the source of overheated connectors.

Problem 1 is the most serious. VFRs route the RR output through a daisy chain of connectors, through a fuse (Main Fuse B in the factory manual) to the positive battery terminal. The battery positive terminal goes to the starter relay via stout wires, where is connected Main Fuse A, supplying the ignition switch and, not insignificantly, the radiator fan. When the fan turns on the stray resistance in the wiring to fuse B form a voltage divider between the RR and the battery, ensuring a dead battery even if the RR is functioning ok. When the fan isn't on the stray resistance confuses the RR about the actual battery voltage.

Problem 2 seems to be more random: sometimes the connections take the current for many years, sometimes they fry in short order. It appears to be a matter of connectors loaded extremely close to limits. The good ones take it, the bad ones don't.

Item 3 seems to be the problem first recognized. RRs get HOT. The alternator on a '98 delivers 34 amps. That current always goes through the RR. The current either is shorted to ground by the regulator or passed on to the bike and battery through the rectifier. Either way, the power dissipated in the RR is 34 amps times 1.4 volts (forward bias on two PN junctions), for a total of 48 watts of dissipation. That's the ideal minimum, actual voltage is more like 2 volts for about 68 watts dissipation. Put your hand on a 70 watt bulb!

Please note, however, the RR does not dissipate the full unused power of the alternator: it only dissipates power of the total current times the internal voltage drop.

There are remedies to all three defects in the VFR charging system. One can re-route wiring, replace connectors and blow harder on the RR 8-) I've done my share of all three!

Here's the detailed version of the story.