I have a 2000 Trail Boss 325. I put the choke on to start it, while it is warming up if I take the choke off, it stalls. So I keep the choke on. After about a minute of running with the choke on, all the sudden it will stall for no reason. Now it will not start with or without the choke. Get this... if I take the gas cap off and blow into the tank (formng a seal with my lips - on the inside...), now with the choke off it will start right up and she is good to go. This happens every time if it is cold. Sounds like a vacume leak, but not sure where to go from here.

 

Check the vent hose on the gas tank for kinks.

 

had some hard starting and stalling issue ,I cleaned the carb and made sure all the passages were open ,and it seemed to help a lot .

 

And being a 2000, you might want to get a new fuel filter. I just got a cheap inline one from the parts store.

 

Thanks for ALL your input... I went out and took the plastic off. The gas tank vent hose is fine. I fired it up with the plastic off and the exact same thing happened. Sooooo, I turned the petcock to reserve and it fired up!!! I am going to let it completly cool down and try starting it tonigh with it on reserve.
I purchased this quad new in Nov 1999 and it has been extremely reliable. I have rolled it at least 4 times and it went solo down a mountain. Replace broken parts and she fires right up. Battery and starter are the only thing that needed to be replaced.

 

Just replaced a few things on mine after a roll. While I had the tank and plastic off, I changed out all the fuel lines. Really need to take the tank off and give it a good cleaning too. Surprising how much of a beating mine has taken and still runs great.