I purchased this engine from Value Hobby along with the 50cc twin. I was a little leary at first because the price was so low. I put it in a Top Flite P51 and was I surprised. At first I could not get it to start by flipping the prop. After some time I decided to put a little fuel through the muffler. It fired right up, just think the diaphram was dry. After the first start no problem flipping to start. Engine ran smooth and had great power. At least as much as the DLE 50cc. Very little vibration and excellent throttle response. I plan to order a couple more of these engines.