Hi all, I have an Hustler 44" Mini-Z with a Kawasaki 19hp engine that has started giving me some headaches. When new this engine literally purred, but for the past 20 or so hours of running time, it has developed an annoying surging at any speed below wide open throttle. The dealer has told me it is everything from normal, to my fault for the gas I use, to me not running the machine flat out all the time. There are times when I need the blade speed a little slower in my yard, and need to run the engine a little slower. I also like to let an engine idle for a minute or two when I start it to warm it up before opening it up to mow. The same is true just prior to shutting it off (Even the Kawasaki manual says to do this.) When this engine is idling, you can hear the RPMs go up and down and actually watch as the governor opens and closes the throttle as the engine sputters off and on. I pulled the plugs and noticed that the one in the cylinder closest to the seat runs noticeably leaner then the other. To pacify the dealer, I have tried different brands of 87 octane, 89 octane, 91 octane and even some 100LL aviation gas I normally use in an antique race boat. I'm sorry but I feel that the dealer is feeding me a line of crap. When he tries the machine he always runs it wide open. When I tell him to idle it down to hear the problem he tells me I should never run the engine below full throttle. I do NOT buy this one bit. My feelings are that the carb is either dirty, or has jetting that is marginally too lean. Anyone have any ideas? I am worried about frying a piston or burning valves. This engine has just under 50 hours on it and has plenty of power. It just won't run right at part throttle or idle. It has a new set of plugs, and the oil has been changed 3 times now and is mobil 1 10W 30. Thanks, Bill B.