I trust you've inspected the carb very thorough. I have no doubts on that.
The ignitions do fail, actually I'm surprised to hear of one that hasn't been changed yet! Never used the rm stator kit for these. Always did Polaris kit. I have used rm stator products and have had good luck with them. If you do use the kit, please reply back if worked. I'll keep thinking, but not seeing it in person can make helping a lot harder.

 

The RM STATOR upgrade kit has at best half of what you need to fix it right. Here's what OPT said a few years ago on another thread about their ignition "fix" for the Sportsman 600/700. "The RM system just uses the charging coil of the original Ducati stator for the ignition source since the charging coil is stronger.Problem is if the charge coil fails you're stuck,have to find another Ducati stator and I have had the charging coils fail before,even before the updated ignition kits were available. To me it's just a cheap bypass of a system that needs to be completely done away with and complete Kokusan kits have been around quite awhile that do this. Buyer beware on this imo."

And " The ignition system changes to a dci ignition whether it's a RM or Kokusan,but they will not work with each other.The RM kits just use part of the Ducati stator for ignition. It's just a patch job or bypass imo. I've read reports on others having problems on the RM kits and like I mentioned if the stator coil goes out on the Ducati you have to find another used Ducati stator since it's NLA from Polaris or just bite the bullet and get the complete Kokusan kit that solves all this with the new stator,flywheel,cdi coil,reg/rectifier,wiring jumpers and instructions.It is the most surefire way of dealing with this problem.Here's one of the best videos out there on installing one also." Search for any of his posts on the RM STATOR band-aid solution versus the Kokusan Ignition Upgrade Kit and you'll find more of the same.


https://atvconnection.com/forums/pol...ition-fix.html

 

This is the kit I was referring to.

https://www.rmstator.com/en_ww/products/rm22957-ac-to-dc-ignition-conversion-for-cdi-and-stator-polaris-sportsman-600-carb-700-carb-2002-2003-2004-2005-2006-rm22957

it completely takes the stator out of the picture
atv magazine did an article on the kit and how good it is.

 

I've been looking for the ATV mag review but haven't found it. As far as completely eliminating the stator, I dont see how that feasible. Something has to tell the machine what location the crank is in(trigger coil, crank sensor, etc.) so timing and firing are correct.

Nice thing about the stock stators, is unless the charge coils go bad, you will be good. If it ever goes bad, I'd assume that rm stator makes one for the kit you may be installing. Hope it cures it, would like to hear the results.

 

I was mistaken when I said it takes stator out of the picture......it uses the trigger coil to fire the ignition . I have tested my stator and trigger coil and it does not pass according to the service manual.....the boos says red to black wire 750-800 and I am ok there but black to ground I have 1.8 and suppose to be 0.

 

I'll look at a wire diagram tomorrow, but honestly 1.8 compared to zero isn't very much. That's actually a pretty good lack of resistance. Also I think the black is a ground, but want to verify. If it is just a ground, I wouldn't think that would be high enough to cause serious issues. I've seen components test 30 or 40 ohms out of spec and never had an issue with performance.

Plus, most of the small wire coils like triggers, exciters, etc usually have at least 120 plus ohms, so the black wire book spec of 0 zero makes me think it's just a ground. Pull the cover off and see where it goes, and look for issues if you like, but I'm guessing it wont be obvious. Nor a problem in my opinion.

 

Yes the black is a ground.

 

So, does this sound more like a possible ignition or carburetion problem? The fact that it backfires when you let off of the throttle makes me think more ignition....

 

Without listening to it personally, I'm still leaning towards carb, only because of experiences I've had in the past.
I'm not saying it is the carb, weird things can happen. I've had in the past a few machines that ran fine, then the next year, ran bad, similar description to your issue, leaned them out and ran great. Cant explain it, but they never showed up for a lean condition after that. Still wonder what changed. Mind you, this is before the cheap carbs available online. Might not help at all.


these are just what I have encountered.
From my experiences- ign always caused a "no spark" problem. Not saying that's all that can happen, just what I've dealt with.

I would still like to see it leaned out on the main jet. May not help at all, but could eliminate that thought.

 

The old plugs looked lean if anything. I have tried choking it when it bogs and Don t help. I have also tried spraying it with starting fluid when it bogs and no difference. It has original 155 main jet in it. Could the slide diaphragm cause this. I have ran it without air box on it and tried to watch the slide and it seems to be moving freely. I have even used a screwdriver to hold the slide open and no difference