I gotta ask Angel, was that the old T.S. with the red head? I run one of their 52's on my S.E. and it has better performance than the Webra 50 I had on it and I can fly for 23 minutes on a 8oz tank of gas. I also have one of their 46's and it's hard to tell any difference between the two engines power wise, now these are the new ones with the silver head and for the price are some of the best 40 to 50 size engines I have ever run. I paid around 60 bucks each and have allready gotten my money out of them (twice). Price aint always everything, Kangke/Tiger Shark sell a great product at an even better price just look at their arf's, and customer service is second to none. Did you send your 40 back? If you didn't you should have, they would have made it right to you, and no I don't work for them I just don't see many people talk about their engines that by the way he could get two of for 120.00 bucks.