I ordered the 2.6cc m12b engine and also the Stirling 16 cylinder propeller engine. First I'd like to start by saying my occupation is generator mechanic... So yes I followed recommendations and know how to troubleshoot an engine. The m12b I received had many electrical issues as well as an imbalanced crankshaft. The Stirling engine ran for about 2 minutes and upon second startup, the weld between the propellor and power shaft broke. I fixed the issue and then noticed during the second run that all of the air transfer tubes were now leaking and thus the engine had little to no power. I emailed customer service about these issues and stated all of the above, and the responses I received back shows me they have no intentions on refunding me or assisting in resolving this. I was however offered a small discount on my next purchase, which I can guarantee I will not be using.