I run e-85 in my kfx. I added 30 percent more fuel on a map that I found that worked good with my exhaust, cam mods. I then tried 40 percent more fuel and its too much fuel. I have a map that works good. I tell you, it starts up alot easier with the e-85. It smells funny too. The biggest problem with e-85 is how much you will go thru if you want to go on a 8-10 hour ride. I have to switch back and forth, esp for our suday ride in 3 hours. If you want my map I can send it to you but there are no guarnantees your setup will work with my file. Its for the PC3. Other than that its ben in my atv for several months and no issues. If I havdto take a guess, most atv manufacturers would know some people mod there atvs and run race fuel. Which may be worse for your atv than ethanol could ever be. So I say run it. One thing about ethanol is that if it ever comes in contact with water in your gas, it will make formic acid and then ur screwed. Its bad. Read it up. If you do run it, the best thing and what I would do is get the bigger gas tank and a dyno tune. The air to fuel ratio is alot different for the ethanol.
p.s. Oh and on the less efficient and makes less power, with an engine that is specifically designed for e85 such as higher compression and with the spark controller, you will make more power. In your stock quad, power output is the same if programmed for it. Once you get that high compression piston and spark controller, by by gas. The rating of octane if it were gas would be approx 102-105 or so than the typical 91-93 that we get out of gas. If you do the math, it will cost you right now, more to run ethanol than gas but its not much, pennies more. Most fuel lines of e85 cars are a specific rubber and they use metal fuel rails. Its not something that I would be worried about. In your car is one thing. You cannot program it as easily, that is where I come in, and your car would run like crap. You are only supposed to run up to 10 percent ethanol in your car and no more. You can void the warrantee. One thing people dont realize is that if your gas contains 10 percent ethanol and you have 10 gallons. 10 percent of that is ethanol right, and you need 30-40 percent more to equal gas to get the right air to fuel ratio, you acutally use more fuel r per say get worse gas mileage when you run that 10 percent ethanol filled gas. You are getting screwed over pretty bad if you do the math.
I am a computer tuner and program gm chevy cadillac gmc pontiac and others all day for custom stuff that includes e85.
Now if you had a turbo, you could make more hp that you would if you ran gas.