I have a Exmark TTHP with a 17HP FH500V Kawasaki engine on it. Sometimes it runs great with full throttle all the time, but others times I will have the throttle up all the way, then I engage the blades and the engine doesn't throttle up all the way. The past couple of days this has happened when I first start the mower, then after about 15 minutes it starts running fine with full throttle. It is very sporadic, sometimes it will just kick into the "full throttle" for a couple of minutes then it will go back to it's low idle stage again. I have changed the oil, oil filter, fuel filter, spark plugs, and I even sprayed a little carb cleaner in the carb. I have tried everything I can think of and It is still happening. It really slows me down because I have to go slow and go over things twice when my mower is running such a low idle. Your advice is greatly appreciated!!