Did I understand you correctly ? you are going to shy away from a K5 because it starts easy ?
Mine always starts easy, two or three kicks cold and first kick warm or hot. And mine has full power, ask anyone who has felt my roost. Seems that easy starting should make you want it more.
If it does have low compression, new rings are a quick and easy fix, this is not expensive like a four stroke rebuild.
But I may have misunderstood you.
John