I have read where others have had problems with their Tower engines. It sounds like TH was decent and took the moter back or replaced it. Lots of flyers that were sent replacement engines said the replacement engine worked great. The factory quality seems to be all over the place on the smaller engines. It seems like the larger engines are better. I have a TH 75 that runs great with tons of power. I have an Evolution 60 engine that ran crappy from the start and gets worse with each run so I am not all that impressed with Evolution. I haven't given up on it yet but I am getting close to it. [8D]