I have an old K&B 45 that came with a used plane. It was totally gummed up when I got it, but a solvent soak was all it took to get it running. Parts are readily available, and while a bit crude in design and not the most powerful motor in its class by far, its performance is acceptable and I have had good responsiveness by the company. its on the shelf right now because the two piece muffler can came apart in mid air and I have not yet replaced it (again, the company assures me the parts are available and there are exploded parts diagrams on their web site). For the price I think they are totally OK