Do you happen to know why they changed the display? Or anything about the previous problems it may have had?
Does "Start" button mean the power button in the center of the button cluster unit?
Has that unit been changed? (if it's a separate part from the display)
What controller does this bike use? I'd guess it's a LiShui (LS-something) if it uses the 800s LCD.
Are the screens the same exact version and model as what originally came with the bike, if you compare to manufacturer documentation or webpages?
If not, they may not be compatible with it due to either firmware differences / protocol, or using a different serial bus type (canbus vs regular serial vs ??)--but even incompatible ones usually power on the system to whatever the controller's default settings are, as long as the connector wiring is identical.
If the connector wiring isn't identical, then because there is both battery voltage (B+ and Lock wires) and 5v signals (TX/RX/etc) in there, it's possible to damage both display and controller so that they will never be able to communicate with each other to do anything (and will not work with any other controller or display either). They'll still power on, and operate within themselves, run the motor, etc., but no talkie anymore.
There are some wiring diagrams for the connectors in this image search; I don't know which ones apply to your controller / displays:
Some bikes use a splitter cable to go from the controller to the various other things on the bike. If yours does, you may be able to get a different version of it with the right connector for your new display. It could even be the cable itself causing the original/new problem(s).
But it may just be easier to find the right version of the display for your controller (or if the controller is the problem, replacing that).
There are a number of displays made in two or more versions for use with different brands of controllers, and these can have different connectors, pinouts, etc. Generally they can't be made compatible with anything else (some might be if using opensource firmware to replace the controller firmware and usually the display firmware, if there is an OSFW for that system).
The hole in the motor casing was probably drilled to allow water to drain out--after a ride, park it with the hole downward. Keeps moisture buildup from corroding the motor inside.
has to be pulled apart to get it into start mode. (Well it used to, now it goes straight to P mode)...
