Just bought brand new an exmark commercial x series 21" w/ bbc. Right upon cold startup the motor surges wile not loading. Engage bbc and it smooths out, disengage and surges. I noticed today while mowing for first 30 min a slight surge. Obviously the motor is warm, and under load so to me this issue warranted a post. Curious what u all think. I know it's a very common mower now and wanted to see how many of you have/had this issue. It should run smooth whether under load or not once at operating temp. My other push mowers have kaws and never do/did this. They don't have the bbc. Does this issue clear up once motor breaks in? Any input is appreciated. I won't be tearing carbs apart etc. seeing as it has no more than 10 hrs.