Greetings,
I had an Evolution when they first came out....Ran great for twenty or so flights. I put the engine in another plane and it wouldnt run at all. I finally pulled the back cover off to clean it out ( It sat for about two months ) and saw that it was missing about five bearings from the race! I sent it back to Horizon, and they sent me a new one!
These engines are not as strong as an O.S. but offer a great value for the price, and are available in the most popular sizes for most planes!
Blair