If the piston wall clearance is too tight an engine can seize under normal operating conditions. It is plausible, but the only way to know would be to measure. An out of round cylinder can also cause tight spots and isn't unlikely given the level of quality most of these kits come with.it's a 1 piece head and the spark plug was a brow colour when I took it out. could it be the the piston and cylinder were too tight as they seemed to have a very tight fit