I have 2 os 30 4 strokes and both have the same problems they are I can take off and fly around for about 10 minutes then land refuel and fly again all of a sudden the motor will either quit on takeoff or fly for 2or 3 minutes and then quit I have been using the same fuel in all my 4 strokes for years with no problems , I have changed the position of my tanks changed fuel lines and god knows what but to no avail my fuel mixture is 15% castor oil 10% nitro and the rest methanol can anyone help thanks in advance