It's not good to do a 12 o'clock wheelie for more than a couple seconds, your warrior is trying to tell you something. The problem is caused by you starving it or flooding it with fuel because carbs aren't designed to work at much more than a 30 degree angle, 90 just isn't possible. Regardless, if it would continue to run, it's hell for the engine. Think about this, if the oil pickup is at the bottom of the engine at the oil drain plug. What happens when you stand it up on the back end and the oil all runs to the back of the engine? Your oil pump is sucking nothing but air and you're running your bushings, bearings, and cam dry.
And yeah, you can put fuel injection on pretty much anything, but there's no bolt-on solution for a warrior. It'll take a lot of time, work, and money to make it happen, probably more than twice what you paid for it. And you'd need somebody skilled in the art of fuel injection conversions to do it, the average person just wouldn't be able to handle all the logistics of it.
