It's called "blow-by". There isn't supposed to be any --- ideally. I think most everyone has some blow-by but, for the most part, most don't notice it because it's small enough not to call attention to itself. Long and short it means that combustion gases are getting forced by the piston and into the crankcase. So, are you using any significant amount of oil?? Have you lost any significant compression ---- are you below the minimum compression --- about 325 psi I think for most Kubota engines??? Is it harder to start??? Has it noticably lost power??? If the answers are "no" to all those questions --- just keep an eye on it. By the way, when you evaluate how significant it is, make sure that the engine is warmed up well and that you've worked it a little bit. Blow-by will be the most significant when the engine is cold.
