This sping I bought a new Exmark 52/23. A couple of months later it starts smoking when it cranks and for a min or two after. It was also burning oil noticably. Well I took it to the shop and at first they said it was a read valve.(I am not mecanical so I have no clue.) They have had it for 2 weeks now and I find out today there is a casting flaw in the block that caused a loss of vacuume in one of the cylinders. So now at about 92 hours I will have a new motor on my Z. Watch out for those thing. Just thought I'd post this incase some one might be having the same problem. they did say that this was not very common happening.