Known for overheating and burning out, often taking the battery with them. Hidden in the cowling of the tail section there isn't a lot of air movement over the R/R.
This is a 60 mm computer fan installed on the R/R. I found this at a surplus store for $2, also available at computer shops for $4.
The mounting nuts were filed down a bit to allow them to be inserted between the cooling fins.
I wound the nuts out near the ends of the bolts, then epoxied them into place. Just as the epoxy was hardening, I removed the bolts and allowed the epoxy to cure overnight. the fan was then mounted permanently with just enough torque to keep the bolts in and not pull out the epoxy.
The fan is wired to the license plate light harness. (My bike has had the fender bobbed and the license plate light removed, so the harness wasn't doing anything anyway.) This brings on the fan any time the ignition is on.
Has this saved my R/R?
I don't know for sure, I'll only know when( if ) the R/R fails. This is the original, it has ~ 50,000 kM on it, the last ~ 40,000 with the fan.
The original R/R never failed, but, I replaced it with an updated Regulator / Rectifier.
This is the Shindengen FH012AA. It's a 50 Amp 3 Phase Rectifier / Regulator. It's still a shunt type regulator, meaning it literally shunts (or short circuits) the input stator. This is still bad for the stator. However, this Rectifier / Regulator is a MOFET based unit rather than the SCR based stock unit. The MOSFET has a much lower forward Voltage than the SCR which in turn means much less power is dissipated in the Regulator.
During a test on a 19 C day, the stock regulator with no fan quickly climbed to 70 C whereas the FH012AA did not reach 40 C.
The FH012AA has other advantages as well;
It is rated for 50 Amps, which means it can be used on pretty much any motorcycle that uses this style of Voltage regulation. Once an SCR has been gated on, it stays on until the Voltage is removed. In this case until the zero cross of the cycle. MOSFETs on the other hand can be gated on and off at any time. This means that at marginal charging the MOSFET regulator can be gated back on part way through the cycle. The outcome is that the FH012AA provides a much better output Voltage at idle. (12.0 - stock, 14.1 - FH012AA on 2000 VFR)
I've installed these units on several bikes with very good results.
(I have no kits in stock)