As follow-up to my previous entry that analyzed the health of the Electrical Charging System on the 1981 Suzuki GS650L.
The conclusion of the previous work was that the stator was functioning properly, but that the original regulator/rectifier (R/R) should be replaced so that when it eventually fails, it does not take out the stator at the same time. A much more expensive repair.
I received my new R/R unit, a SH775 – Polaris part number 4012941, from Partzilla.com. This a very common unit used as a replacement for the older bikes. I also ordered a wiring harness kit from Eastern Beaver for this unit. What I didn’t notice when placing the order was that Eastern Beaver was located in Japan so it took more than a week for the wiring harness to arrive at my address.
Here is the new SH775 unit on the left with the original R/R on the right.
The new unit is larger in all dimensions than the original, but the mounting hole pattern is the same. My installation slowed down again as the the original mounting bolts were now too short to install the replacement unit requiring a quick trip to the hardware store for 86 cents worth of new bolts.
And here is the wiring harness and R/R before installing under the the battery box and air filter box.
The R/R and harness are a 5 wire unit which matches the original equipment. The three yellow wires to be connected directly to the stator, the red/positive wire connected to the hot side of the wiring harness going through the fuse panel, and the black/negative wire connected directly to the negative terminal of the battery. I also have a wire from the negative battery terminal to one of the bolts for the R/R mounting as a common ground point for my coil relay mod and any future electrical modifications.
Here is the R/R and wiring harnesses remounted into the location below the battery box.
Then it was just snaking the wires up and making the connections. In the original wiring harness, one leg of the stator runs through the headlight switch which is a holdover from when the motorcycles did not have their headlights always on. If the headlight was switched off, it would disconnect one leg of the stator and only require 2/3 of the stator voltage to be regulated while there was less electrical load being used. My headlight is always on, so I eliminated this connection and just used direct wiring of the R/R to the stator. More old wire and connections removed from the electrical system.
I ran through the stator tests again after replacement of the R/R and my new wiring. All results were similar to what was seen previously except for the voltage reading at 5,000 RPM’s. This reading was lower than spec with the original R/R. The new R/R produced a reading of 14.3 volts at 5,000 RPM which is within the range specified and 1.2 volts better than previous. I feel better now that the battery will be effectively charging while out riding.
I put the fuel tank back on and prepared for a quick test ride around the neighborhood to try out the coil relay mod and R/R replacement. The quick ride turned into a 40 mile ride. It was very enjoyable for my first extended ride on this bike. The only part not working well was the tachometer reading which jumped around during acceleration.