The symptons your describing are of the motor being run too lean. You run the motor at half to full throttle and after a few minutes the motor heats up and starts to lose power because it is not getting lubrication. Then you land and let the motor idle, the motor starts cooling and then it is Ok till youi give it power again and start the process all over. I would think your about 1/4 to 1/2 turn too lean on the main needle. I have helped several using the TT 36 with many different kinds of fuel and this seem to be the case on most of them.

David