I just purchased not to long ago a 2002 Exmark Lazer Z HP 52" with a Kholer 23HP (CV23S) engine. It was just a insane deal I couldn't pass it up but I am not a huge Kholer fan... Basically it was an old farmer mower and only has 600 hours and it has some small cosmetic issues which I am dealing with. Also when I got it, it will only start close to full throttle. Now I did a full tune up including new plugs, air filter, oil/filter, fuel filter, battery, and a good ole cleaning. Now it will throttle down to half power but any further it cuts off in a few seconds. Any suggestions? should I run some Sea Foam through it to clear the carb and see how it does? Or is there any issues that people have from their experience with this motor that may cause this. To me I think it is getting too much fuel myself.... It back fires sometime when I shut it down and it has once or twice when running for no reason.... Also 1 more thing I notice when I tuned it up, that the left plug was worse than the right (Directs from looking at the back of the mower). I do not know if the plug on the right was replace? or if that would be a sign of my issues. Any thoughts with small stuff to try first. I am pretty sure it is in the carburetor but I may be completely wrong. Anyways I have less than $1000 in this mower and it would be great to get it running right to add as a back mower for myself.