It's absolutely amazing, the number of ways well-intentioned folk can screw up a Rotax 9xx engine. This is a little high-tech jewel of an engine with aluminum heads, cylinders, pistons & crankcase. It requires proper and knowledgeable care and feeding to operate happily. When given this kind of care, it will last for 1500+ hours at 5000+ RPM. If you don't provide proper and knowledgeable care and feeding the results are ugly and expensive.