I am new to this forum and website. I am MTGunner from NW Montana. I am experiencing performance problems with my 2004 Sportsman. I bought my '04 Polaris new and have near 7000 miles on it currently. It will not accelerate normally in high range. It bogs down trying to accelerate and back fires. It has good power in low range. I have installed a new plug. Installed a new inline fuel filter. I pulled the bowl off the carb to check for sediment. Nothing. I pulled the main jet to verify no blockage or obstructions. Nothing. I run a K&N air filter that has been serviced last summer. I have added new fuel to asure no problems with bad fuel. I started having problems during plowing snow this past week. I will say that I have plowed LOTS of snow these past 2 weeks and hope that I have not pushed it to much. I am at my limit for answers. Looking for solutions and perhaps a fix. Thanks in advance for any help from this forum. MTG

 

Do a compression test. See if the motor needs a refreshing, not a big or expensive deal on a 2 stroke as it is on a 4 stroke.

Not familiar with your 400s specs but on my 2 stroke sled, 125-130lbs is about new and a top end rebuild is needed at about 105-110 lbs.