Have about 4+ tanks through Thunder Tiger .61 PRO and WHEN it runs - it runs GREAT!!!!

Problem is that it is almost impossible to start - can't seem to prime the engine as it won't pull fuel from the tank. I have a tail drag SIG 4* 60 with DuBro fuel tank - I've checked everything 3 times and the fuel line system is air tight.

When it FINALLY starts - runs perfectly for one tank and then after refueling leads to dead sticks - runs fine until right after takeoff and then quits.

HELP????