Honda uses K-line on the rebel, and pre '19 cb500f/r/x.
Of you're only after the info through the DLC port, the easiest wat to do so is via a lonelec cable, an elm bluetooth dongle and some mobile software (I use torque pro) to log vital data.
If you're after more sophisticated stuff, and want to implement it yourself, search for HondaEcu on github. Project is to read and write honda ecu bins, but part of the code is for data logging and display so you can use those parts in your implementation.
I know the developer (also caller Ryan like I assume you from your nick) very well, and work with him on testing and feedback. I've also thought about the idea originally to create a display with gear, coolant temp and rev indicators, but never went that way as I could solve my needs otherwise.
Currently building a data logger though around the hondaecu codebase, using a raspi zero connected to the dlc port, a wideband O2 sensor and a gps/giro to do autotune for the ecu flashes.
Hope this helps.
Also sending a PM with my email so you can contact me directly - I'd kike to hear more about your progress.