2017 Z800 - changed the coolant.
I have read for years of people having trouble after changing their coolant on these machines and I did not understand until I saw some youtube videos on how NOT to change your coolant on these machines.
For instance, Red Neck garage has a video where he disconnects a couple of hoses which is completely unnecessary, more difficult, and messy.
By the book:
Loosen the coolant drain plug at the bottom of the water pump and let it leak out.
When it's done draining, remove the plug and jack up the front end a few inches.
When the draining stops, put the plug back in, and fill with distilled water to flush.
Run the engine for a few minutes until the engine warms up or the fan goes on.
Repeat the drain procedure.
Now, the plug has a copper washer. If that washer has any deformities, either sand it flat or replace it.
Torque the plug into place (89 inch/pounds).
Fill with 3.1 quarts of your choice of coolant (50/50).
Start the motor and let the system burp.
Top off the radiator, put the cap on, and add some coolant to the overflow bottle.
I did not have to use the vent screws on the heads to let the air out.
Drop the front end and take it for a ride!
I used Zerex G05 (Gold/Yellow color), a HOAT coolant (with silicates) for aluminum engines/radiators.
Prestone OAT coolants are fine as well as most modern coolants, but they lack silicates. Avoid IAT coolants, which are usually green in color, and what came from the factory. While they have silicates, they don't have the protection longevity of modern coolants.