:( I have a 97 Arctic Cat 600 EXT, It has the ZRT 600 triple engine. I was up in Marionville this weekend and started to ride the loop, it ran great! Then it warmed up and appeared to foul a plug, so rather than guess(because they all looked clean) I put three new plugs in it. This didn't seem to fix it. I started to wonder if the plug wires were getting too wet from the snow spray that was coming off the other sleds...so I led for a while and got on trail 19...at top speeds there was no problem, but the minute that I slowed or stopped the engine would almost stop and would become sluggish at slower speeds. I tried to figure out what plug was missing...but it appeared to be a combination of any two at any particular time.
Has anyone ever had a coil(s) go bad on these? Or do these things just eat plugs? One person I talked to said I could even be loosing a cylinder? Any thoughts or help?

Well, ice in the fuel system, maybe?? Carbs clean? How old is the gas? Anyone else?

well, first thing to check would be, are the carb. switches still connected, check the tether if it has one, try by-passin the carb. switches, check the chokes, make sure 1 is not holdin up in carb, could cause the choke to be on either carb. also i've seen the cables go bad on chokes, frayin inside of caseings, holdin up either chokes, make sure carbs are all synced together, key switch can also do funky things, check the engine grounds, make sure that the ground strap from the recoil to the exhaust silencer is mounted under the brakett, these engine run a normally close ignition system and have to have good ground, so check all grounds, i even added another ground strap to my engine, from where the cdi and stator ground to the mag side of engine to the chassis.check all these things out, and let us know how ya made out

Had a similar problem with my brother's 02 ZRT600, and had a similar problem with my 98EXT triple and my nephew's Z370, you may need to put the up-date white plastic bushings in the throttle handle, there is a switch in the connected to the thro lever that gives a lot of problems. Simple to do, remove the throttle pin and replace the bushings, be sure to put them in the right way. To test if that is the problem disconnect the kill switch at the handle bar pad, which should by-pass both.
I also by-passed all my carb switches and left them that way.

I agree with bypassing the carb switches,,, I know they are for the better, but I have had preblems with mine and just bypassed them,,, have had no problems since,,, when it runs like that, if you hit the choke,,,what happens????