The GSXR’s seem to be plagued with speedo problems. On this particular bike, the owner has tried to replace the speed sensor and the speedo cluster. Swapping these components did not resolve the issue.
Here is a pic of the cluster, where the speedo, tach, and fuel light are not functioning:
Armed with the wiring diagram located in the service manual and a multimeter, I had a feeling the problem had to be located in the harness. After removing the fairings, the problem was very apparent. The unsealed connector located on the left side was corroded!
The red/blue wire was hanging on by a strand! I made an attempt to locate the factory plug/receptacle & pins. It was nearly impossible, and I bet the cost would have changed my mind anyway. The wire was repaired using AMP Faston quick connect spade terminals.
Any remaining corrosion was cleaned with CRC Electronic Cleaner. Here is a pic of what a properly functioning speedo cluster looks like: