Stalling on 2007 KFX 90

[kdsd731]

I am working on a 2007 kfx 90. The owner has had the restricters removed. His complaint is that when riding wide open the unit will stall eventually. I have added a clear hose to the carb drain to observe the fuel level both running and stopped. I lifted the rear wheels off the ground and held it wide open. I watched the fuel level go down until it stalls. for the first 25 seconds or so, the fuel level remains high, then it steadily starts dropping and by 35 seconds it stalls. The carb is clean, the float height is good. Fuel lines are not kinked. The petcock is clean. The fuel filter is clean. The gas cap is venting properly. The fuel flow into the petcock is very good. After it is significantly slower, however is believe this is due to the petcocks design. I by passed the petcock and ran the hose from the tank to the carb and had great fuel flow. I held it wide open and the fuel level was decreasing but a lot slower. Any suggestions on why it runs dry?