Hi everyone! Long time lurker, first time posting. Overall I have been able to solve many problems using this forum and thanks to everyone who have helped me out already.

I have a 2004 Sportsman 500 that can idle properly, but under any load it bogs down, backfires, dies, no power, etc. Checking the sparkplug, it is very black. I believe it is running rich.

So here is the history . The Sportsman 500 was sitting in the shed since 2009 because it died while on a ride and we never managed to fully look into it. It had no spark and I was able to determine that it was because the pulsar coil was misaligned. It was misaligned by a lot because the recoil broke, broke a hole in the casing, and I assume that one of the ears on the recoil that I found inside the casing likely smacked the pulsar coil because it was about half an inch out of alignment. I ordered a new aftermarket pulsar coil and recoil+casing. I didn't replace the pulsar coil yet, because while I was waiting for shipping, I checked the ohms (~195 I believe) and bent it back into place and verified the distance was 0.04" I believe. I also installed the new recoil+casing.

After "fixing" the existing pulsar coil, I had the one spark no spark issue. I cut the black wire from the CDI and that resolved that issue. I was planning on addressing that much later. Now when someone tried looking at this before, they lost a couple carb parts for the throttle, so I ordered an aftermarket chinese carb. I took out the OEM carb and it was clean, including all the jets, orings, and seals. I used the couple throttle parts from the chinese carb and put it all back together and I was able to get it to idle and it seemed to work going up and down my back lane, but I didn't really press it. When I got it back out to the farm, I had the bogging down issues. At first I thought it was because the carb may be bad, so I switched to the chinese carb and it had identical issues. I have since switched back and forth several times with the exact same results. I have also tried replacing the fuel pump with an aftermarket one with the same results. All fuel lines and the air line to the pump are verified clean.

Now, one concern I have is the hoses that attach to the carb(s). There is the gas input, the air line to the fuel pump, the main part that connects tot he air filter. There is also an air input that goes down to the bowl and float on the throttle side of the carb. I am not sure what that is supposed to connect to. On the chinese carb, the input is on both sides. Plugging that makes it so I can't even start the ATV. I also just ordered a new air filter because this one was filthy. The results were the same both with the filthy filter and without a filter. I also have the two lines that go into the filter, one that is blowing air and the other one.

According to the service manual, they most likely culprit is the carb, but with the symptoms being identical (unless I am missing something air pressure related with that air input to the bowl), I am thinking that isn't the case. The service manual also suggests the coil system. My next step was to try with the new air filter, which I am not overly hopeful for. Then, I will replace the pulsar coil, because I am hoping that maybe it just isn't sparking well enough? BTW it is a new spark plug, and I have another new one, but I am hesitant to put it in until I have figured out the issue.

Sorry for the wall of text. Hopefully someone can shed some light, and I will also keep this updated for anyone else. I did notice another post on a different forum with identical symptoms that was never resolved (from 2011).

Thanks!

 

Update:
So I replaced the air filter, and with the replacement Chinese carb in there, I attached two hoses to the air vents on the side of the carb (which the OEM has only one air vent on the fuel line side) and ran them up beside the fuel tank and that is all. It seems to run fairly well. full power, no breaking down when I pin it (up and down the back lane again). If I go half throttle there is some small break down but then it seems to correct. I am thinking that maaaaaaay be cheap carb issues. Not sure yet. Taking it somewhere close for a spin tomorrow.

 

OK, so I took it for a spin and it was still breaking down. I figured, screw it, I'll put in the new pulsar coil. After taking things apart and pulling off the flywheel (damaged my puller... damn), I was able to see the stator and get to the screws for the pulsar coil. Well, the stator had a post that was slightly damaged and the wires were crumbling and exposed. Here is a pic:

So obviously that would cause issues. I ordered a new stator from RMStator here.

As a side note, I also replaced the pulsar coil while I was in there. Now I couldn't find any information about the polarity of the pulsar coil, so I am not sure if it was installed properly as the pulsar coil I bought (200 ohms) was blue and green wires, not the white and white/red cables. After installing it and putting things back together, I wasn't able to even get it started anymore, but I didn't check spark yet. I believe the gap was ok, and it may be because the wires in the stator that were touched and started crumbling.

 

OK, so I took it for a spin and it was still breaking down. I figured, screw it, I'll put in the new pulsar coil. After taking things apart and pulling off the flywheel (damaged my puller... damn), I was able to see the stator and get to the screws for the pulsar coil. Well, the stator had a post that was slightly damaged and the wires were crumbling and exposed. Here is a pic:

So obviously that would cause issues. I ordered a new stator from RMStator here.

As a side note, I also replaced the pulsar coil while I was in there. Now I couldn't find any information about the polarity of the pulsar coil, so I am not sure if it was installed properly as the pulsar coil I bought (200 ohms) was blue and green wires, not the white and white/red cables. After installing it and putting things back together, I wasn't able to even get it started anymore, but I didn't check spark yet. I believe the gap was ok, and it may be because the wires in the stator that were touched and started crumbling.

 

So, I put the new stator in... and it works great! I am happy with the RMstator kit, good price and it all fit well and I love the fact it had all the wiring harnesses etc. Plug and play. The only things I needed to do were drill out the holes in the pulsar coil mount a bit to make sure the gap was within range, cut 2 zip ties holding the wires to the stator (it was too short), and put the ECM plugs into the existing harness. Overall the wires were a touch shorter so a bit more of a stretch but oh well. Everything now runs great, and it looks like my odometer is working properly now, which it hadn't for a long time. I guess it wasn't getting the right voltage for a long time and that's why that wasn't working well.