There are a couple of threads in this forum about "tank lock"--where the tiny vent line on the gas tank either is blocked or inadequate to compensate for the amount of gasoline being used. It causes a vacuum in the gas tank and your carb starves. In some cases (mine, for instance) if makes the quad quit. The quick solution is to unscrew the fuel cap. The more involved one is to replace the cap with a vent cap.

However, your spark plug indicates a rich mixture, not a lack of gas, so this may not be your problem.

 

I vote for tank lock. Deskbound mentioned the spark plug test indicated rich mixture, not lean, but it will show that if it is jetted a little 'fat' through midrange, and only leans out at full throttle for extended periods of time. Trace the fuel line vent, remove the cap, and blow compressed air through the line. Yes, I know if there is a blob of gunk in it, it will wind up in the gas tank, but that is easier than trying to blow it 'out'. I suppose you could get to the connection at the tank if you took some plastic off.

 

I believe that it was Floor Runner or Gregg Sims that posted this originally. Perhaps it will be of help to some


The purpose of the Polaris ETC is vaguely described in the manual. The way I understand it, it's supposed to shut down the ignition system in the case of a stuck or frozen throttle cable. Either way, it's a safety device, and like most all safety devices it complicates an otherwise simple, straightforward system.

Slack in the throttle cable "fools" one of the two switches in the ETC into briefly actuating ignition shut-down, usually evidenced by a backfire on quick deceleration. The other common problem created by a stretched cable is the machine's refusal to idle. Fortunately the adjustment procedure doesn't require tools and is fairly simple, even though it may require several tries to get it just right.

Check the amount of freeplay you have in your throttle "paddle" (thumb throttle) before you feel it start to pull on the cable. You shouldn't have any, or 1/4" at most. It depends on the machine, each is a little different. Just down from the ETC box on the throttle cable you'll see a plastic sheath covering the cable adjustment mechanism. Carefully slide the top sheath up the cable and the bottom sheath down the cable to expose the adjuster. This is a simple arrangement that increases or decreases the cable's slack by lengthening or shortening the sheath it's in. Loosen the little knurled jamb nut that holds the adjuster in place and rotate the adjuster clockwise to increase the cable's slack (shortens the sheath) or counterclockwise to decrease the cable's slack (lengthens the sheath). A little turn can have a big effect so take it easy. Be sure your handlebars are pointing straight ahead when making these adjustments. Your cable should be tight enough that you have little or no freeplay in the paddle but not so tight that you raise your idle when adjusting it. When you have it where you think you want it tighten the jamb nut to hold it there and test drive.

Pulling on the cable sheath will naturally increase "idle", as it mimics your pushing on the thumb throttle. One mechanic told me he knows when the cable is adjusted right when the idle increases just a bit when the bars are turned to the extreme right (this pulls on the cable a bit). However you do it, you may also have to adjust the idle. There is a big gold thumb screw at the bottom of the carb for this and clear instructions are in the manual. If you have to crank this up temporarily to keep it from dying while adjusting the cable, then readjust it to the proper specs when the cable is correct.

These are minor adjustments that have predictable results. They won't correct or compensate for other problems. I'd start by draining at least a cup of gas through the float bowl drain then add some carb cleaner to the fuel. After that make adjustments a little at a time and see what you get.
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