I put a rebuild kit in my 400 Xplorer last summer, seemed to run ok until I tried to run it near or at WOT for more than a couple of minutes. 3/4 throttle or less it runs just fine, when I go WOT it will run great for about 1-2 minutes then acts like someone shut off the fuel. If you wait about 20-30 seconds while idling you can repeat the process anytime with the same results. I have checked the items below.

1. Replaced fuel filter
2. Checked the flow from gas tank/vent lines.
3. Floats don't appear to be getting stuck.
4. Running a 210 main jet, all other settings are stock.

Any other suggestions would be great, as trail riding like this gets old fast!!

 

what elevation are you at, did you go richer on the main jet, does it idle fine, does it fun better with the choke on, pull the airbox lid and see if that helps, my normal questions for what it's doing

 

Check the vent lines again