I have a 2000 Polaris Trailblazer 250, I just bought it and took on some trails it did fine until I tried to climb a steep hill it spit and sputtered and came to a complete stop and when I gave it throttle it just bogged down and wouldn't move, what would cause that? on flat land it runs great but only going up steep hills it would bog down?  

We had the same but it wasn't just on hills you rev it and every thing but as soon as you got on it and try to get into it hard it wouldn't it just bog down and it ended up being the air filter and the sock were bad washed out the sock and replaced the filter ad been good since  

I've got a 2003 trailblazer.  Same problem - Out of the blue, I tried riding it and it would start and idle fine, but when I got on it, put it in gear, and hit the gas, it bogs down and stalls.  Did you change the filter and foam sleeve?  Did it solve your problem?  

My 2000 Trail Boss 325 does this exact same thing. I pulled the carb last week and cleaned it all thoroughly, but that didn't solve it. I figured I'd try the air filter and fuel filter next. Mine will usually rev up find when in neutral, but under any sort of load it just bogs down, and it fouls plugs like you wouldn't believe. After just a few minutes, they are covered in carbon.