I have a problem with fuel not staying in the fuel line from tank to the pump,you can see the fuel draining back to the tank and a lot of air pockets,raplaced fuel pump,filter is on the frame rail and it pulses from crankcase,you can fill the line by blowing in the tank,motor runs good for about 6 laps and starts loosing fuel when back to the pits the fuel lines are empty any ideas? thanks