I have 2008 X728 with 230 hours. Whenever I start the tractor...I start it according to the manual, between 1/2 and 3/4 throttle with the switch in the on position for a few seconds to let the system build pressure. It seems to me excessive cranking when the engine is cold. I started timing the cranking, and I let it crank for 5 seconds, and then let it set for a minute...and then another 5 seconds of cranking it will start. Pretty much the same thing every time the engine is cold. After the engine warms up, it starts great...pretty much instantly when you touch the key. Also, after the engine is warm...when going from full throttle to 1/2 or lower throttle...the engine seems to miss and cut out if you don't cut the throttle down extremely slow. I also get backfiring sometimes while starting the engine cold. Recently had 200 hour service done, with new spark plugs put in it. 10 hours after the new plugs...I had taken the tractor in for another issue to a different dealer, that was closer...and they said the engine was surging and needed the plugs changed. The tractor is still under warranty, so if not something simple, I am going to take it back to the dealer to see if they can come up with anything. Any help would be appreciated.