I currently have a crf250 on my birel shifter chassis and im having an issue with fuel. So i can ride it easy for 5-6 laps or completely hard for 5-6 laps and around that time frame i get hesitation and the engine will stall out. When it does this if i look at my fuel line from the outlet of my fuel pump to the inlet of the carburetor it will be half way full of air so for some random reason i start getting air in my fuel line. It will start right back up afterwards and will run halfway decent. If i let it all sit for awhile say 15 minutes i can ride for another 5-6 laps straight without any issues. My fuel line isnt near any heat source thats heating it up over time as ive looked that over. Checked to make sure all my lines are connected properly and tight to make sure its not sucking in air and getting it in my line. The entire rest of my fuel line from tank through filter to pump is also always completely full no air. Just air from pump outlet to carb inlet hence why it starves for fuel and then dies. My fuel pump is a Mikuni round pump with 2 outlets so one is my return of course. Any ideas whats going on or is it possible my new fuel pump is bad and has some issues where i need to order another fuel pump? Whats the best option or whats the most common fuel pump used to run these 250cc karts?
Sorry for the delayed response as Ive been overwhelmed with work but this last weekend I did get an opportunity to check the kart over once again and I took your advice and rechecked the fuel vent….it was plugged indeed. Cleared it out and took it out and it ran perfect the entire day. Thanks again for the quick response and the helpful advice.