The Charging system

The combination of Permanent Magnet rotor/stator, oldfashioned design of voltage regulator and rectifier, and 35+ year old aging wiring on the GS bikes is becoming a problem regularly.
This causes issues like blown stators, regulators and rectifiers.
Sometimes other components subsequently fail when things go wrong. 

This issue has led the members of The GS Resources forum to start "The Stator Pages".
These pages not only provide a good way to diagnose issues with your charging system, but they also discuss solutions and alternatives to the original setup.
Highly recommended !

visit THE STATOR PAGES GS Charging System Health check GS Charging System QUICK check OEM-Compu-Fire / Shunt-Series comparison
mobirise.com

Compu-Fire 55402

There are many threads on The GS Resources (GSR) forum discussing alternatives to the original shunt-type Regulator/Rectifier system (RR).


Popular replacements are the series types Shindengen SH-775 and  Compu-Fire 55402. 

Both very reliable, good replacements that many GSR members have been using without issues for years.

The Shindengen used to be low price, but lately they upped the price considerably.

Long story short - i chose the Compu-Fire 55402.


It's "series" switching design is superior over the original "shunt" RR and the Shindengen SH-775 which means it does draw way less power from the generator, and generates less heat. This results in a longer lifespan for stator and RR.


Installing the Compu-Fire RR involves some alteration to the wiring harness, further improving safety and reliability.

The 40A main fuse can be replaced by a 15A fuse.

This shows the impact the replacement RR has : large amounts of current are not converted into heat anymore, relieving the stator and RR.

GSR Posplayr (Jim) : "My calculations are it is in excess of a 200W differential. 125W with SERIES and 350 watts with SHUNT in the stator."


http://www.thegsresources.com/_forum/showthread.php?191795-GS-Stator&p=2252264#post2252264


I know I have never described this but it is basically first principles of electrical engineering. The TOTAL power generated by the charging systems can be divided logically, physically and analytically into three components. Power dissipation in:


The stator (350W shunt v.s. 125 watts SERIES)

The R/R (25-50 watts depending upon SHUNT SCR (highest) v.s. MOSFET (lower) v.s. SERIES SCR (SH-775) and the lowest being MOSFET SERIES(Compufire))

The load (including the all electrical components and the battery) is what is specified in the manual and is generally 14-15 amps at 14.5V or 203-217.5watts delivered.



Strictly speaking you can add the wiring between the R/R and the battery as a separate item from the load as well.The Spec sheet only gives you the rating for item #3. Items #1 and #2 are not specified.


What I described, calculated and documented is item #1. For shunt it is 350 watts.


I would have to look up the specific voltage drops to estimate what #2 is but I don't have those figures readily at hand. Regardless it is also not specified.


Jim


LEARN MORE

Testing the Compu-Fire 55402

Compu-Fire installation instructions (does not cover the 55402/55403) contain below procedure. Compu-Fire tech support kindly confirmed this to be applicable for the 55402 also.
I intend to install a very small 3-digit voltmeter to always know what is happening in the charging system.

TROUBLE SHOOTING
Do not use test procedure found in the factory shop manual.
The Compu-Fire voltage regulator uses high efficiency series circuitry.
The electronic circuitry is completely different.

With the main switch OFF, measure the voltage from the regulator output terminal to ground.
The reading should be 12 - 13 volts.
If there is no voltage reading, the battery is disconnected.

Start the engine and bring the RPM to 1500.
The voltage should rise 1/2 to 1 volt.
This indicates that the voltage regulator is charging.
This completes the test.

Cool(er) Runnings

The design of the Compu-Fire draws less amps from the stator and dumps less amps back into the stator. These things should mean it is generating less heat than the standard setup.
Several GSR forum members reported a notable drop in oil temperature after mounting a Compu-Fire 55402.
Interesting read of the lower temperature on an Aprilia : 
http://www.raven.apriliaforum.net/wiki/index.php?title=Ersatz_Spannungsregler

The GS does not have much oil flow in the stator area, so the effect may not be that big.

IR view of the original R/R

IR view of the Compu-Fire 55402

IR view of stator cover using original R/R

IR view of stator cover using the Compu-Fire 55402 R/R