Why did my 86' samurai speedometer and temp gauge stop working but fuel and rpm gauge still work fine?

The issue with your 1986 Samurai's speedometer and temperature gauge may be due to a malfunctioning speed sensor or a broken connection in the wiring specific to those gauges. It's also possible that the gauges themselves have failed or that there's a problem with the instrument cluster. Since the fuel and RPM gauges are functioning, it suggests that the power supply and ground connection for the cluster are intact. Consider checking the wiring, fuses, and connections related to the speedometer and temperature gauge.