I have been struggling with a problem on my Polaris atv for about 3 years now, heres a description of my problem from about a year ago:

It is a 91 Polaris Trail Boss (4x4) that I put a new piston in. Everything runs great, except it likes to bog down when you first warm up the engine. Its fine while its cold, and runs okay after getting the engine hot (maybe after about 25-30 min). It will also run okay if you keep the engine reved up high, but if you slow down to change to reverse, a sandy/rough spot, or let it idle for a bit, then it gets into this rut where it just sits and idles. It wont completely die, but it bogs out if you try to give it gas. I have found that if it gets into this bogging rut and I push the starter switch (with the engine running) it will snap out and start running as long as you don't let the rpm go to low. I'm afraid I'm ruining my starter though.

Now here is an update from my recent work on it:

As I guessed, my starter is failing from having to push the button when the 250 polaris starts bogging out. Several interesting facts to add though. First, I forgot to mention that it backfires as well as bogs out. Second, for whatever reason this whole problem went away during the winter when it was colder. I live in the New Mexico desert so it doesn't stay super cold the whole time, but we can easily get down to single digit degrees (yes Fahrenheit). The summers here are hot and dry though, and that is when the problem has now resumed. I was told this could be a jetting issue, so i got two jets, each a size lower, and have played around with the carb. I've adjusted jets, air/fuel screw, the needle, everything i can think of, but nothing really effected it. Now for my third discovery. Up til yesterday, I definitely thought it was a carb issue. To make a long story short, I took the battery out, and it stopped bogging out on me! At least for a short drive, it ran fine. However, when i turned on the 4x4 button, it started bogging out again in similar fashion. So now i have a feeling that it is an electrical problem.

Anyone with some helpful ideas? I'd appreciate any advice, cause this thing is driving me nuts!! Thanks.

 

Have to have the battery for the 4 wheel drive to operate. Keep the battery hooked up or you can blow bulbs along with damage to other components. Pull the black wire from the reverse limiter and see if it helps on the bog. If it doesn't I'd recheck compression when it's warm compared to what it reads cold and see if there's a drop. Plus simpler to just rebuild the carb if you haven't done so and eliminate it as a problem.Carb Rebuild Polaris Kit Trail Boss 250 2x4 4x4 89 90 91 92 93 94 95 96 97 98 99 | eBay
Plus most people over look crank seals that may leak and cause problems.Can either cause erratic idle or bogging condition. Reverse limiter is Item #33 on the break down link.They can cause limiting/bogging problems in forward range if they start to short out as most of them do. Black wire goes to the circuit board under the tank cover.just pull it and tuck out of the way. You'll have full power in reverse also without having to push the over ride button.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

Wow! This sounds like what i might have been missing all along. And thanks for the tip on the battery. Your awesome! On the carb rebuild, what groove should i start the needle at?

 

Stock needle clip position is usually 3rd slot from the top.Start at that.

 

So i think the problem has been fixed on my four wheeler! Yes! Thanks to polaris tech. I owe you big time for the tip on the reverse limiter. I think that has been my problem all along! ugh!

Now I'm trying to adjust the carburetor after my recent rebuild and know that i have the bogging issue taken care of. I have a manuel that tells me the defaults of all the adjustments. Do i just set it at default and try to run it there? If so, my manuel says at the altitude and temperature I'm at, I should put a 125 main jet, but the lowest i have is a 145-can i run it at a 145 main jet, or should i get a 125? Also, my biggest fear is running the machine to lean and blowing my engine. What do i listen for to avoid that? Any tips on adjusting 2 stroke carbs would be greatly appreciated!

 

Your manual should show an altitude/temperature chart on basic jetting that you can start at.If it doesn't look at this one in the engine section.http://gh-ftp.com/ORV%20Manuals/Pola...e%20Manual.pdf Hotter temps,richer they run,but have to consider altitude in this also.The chart will help,but always plug chop it on jetting changes. Warm it up,at a high speed kill it and check the color of the plug. If whitish color,jetting too lean, light to medium tan/brown is what you're aiming for.