[Water Warrior 2]

My first thought would be a corroded and stuck choke cable. I would start by disconnecting the cable at the carb and cycling the choke lever for smoothness and cable movement. Any light oil or ATF will lube the cable and wash out some of the grunge. After that I would inspect the choke itself for proper function. Keep it simple and don't go looking for exotic problems and fixes because there probably won't be one.
If your bike really has that few miles on it in 5 years I would expect a lot of TLC to make things smooth and dependable again. We are here to help.