I have a 2007 exmark lazer z with a kohler 27hp cv740 (unknown hours. Hour meter stopped working at 1250) The engine is blowing white smoke at idle and when throttling down but does not blow smoke at full throttle. It also uses a lot of oil. I did a compression test and one cylinder has 150 psi and the other one has 130. The cylinder with lower compression has a really fouled plug covered in gunk but the cylinder with good compression spark plug looks clean. While the engine was running I pulled the dip stick to add oil and it started spraying oil and smoking out of the dipstick tube. I'm thinking it could be the rings or a head gasket?