The flame on the burners is dark blue, and on 3 of the 4 burners it is a very small flame even with the knob at the highest setting. If I remove the black center cap from the burner, the flame is about 8 inches high, like a bunson burner, with a yellow part at the bottom and a lighter blue at the top. However as soon as I replace the cap, the flame reduces to a small, deep blue flicker. I can't seem to find any adjustment on this range at all.