I have broke in 5 of the 2.18 MDS 2.18 engines for Fellow flyer's.Out of the 5 only one ran descent. 2 had such vibration issues while running on the stand we couldn't see or adjust the High end needle valve, before you even ask yes the props were balanced perfectly One seized at the beginning of the 2nd tank of fuel, and no we did not over heat the motor, at no time did we get the engine above 195 degrees. After further investigation of why the engine seized we discovered a piece of the engine casting had chipped off and seized the crank to the block, Why we asked. I looked at the area that was chipped with an eye piece I use at work in metallurgy. I found I stress riser caused by a dull chattering tool die used in the machining process.On to the last engine about 1/2 way through the first tank of fuel the RPMs started to drop off rather sharp. I pulled the fuel line to stop the engine. after checking the problem we found small flakes of aluminum had scored the piston and cylinder liner that were sucked in and had come out of the uncleaned carb. Know if that is not very bad quality control I do not know what you would call it!!! But you guys are right about one thing Horizon is good about getting another one out to the poor soles that could have been flying rather than worrying about the next engine being sent to them!! Maybe You have had better luck with MDS but I for one will never buy one!