Paul, the old DOC here, I have two of each of the Brodak 40 & 25. The 40 was broken in per instructions an has been a great engine for the price. The other 40 is still being broken in. The first 25 was ran on the bench 3 times and then put on the Brodak Mauler. The grandaughter has been flying the combination since. The last time out she was doing loops. I have put the combination thru a full pattern several times. I use Sig 10% fuel, Top Flite Power Point 10-4 prop and a 4 ounce clunk with uni-flo setup. Also it is flown on .012 X 60 center of handle to center of plane. The second 25 has several tanks on the bench and is ready to go in an airplane as soon as Bob Z. and John B. get the little bird out that was designed around the engine. Later, DOC Holliday