Hi all, I have a Bobcat Walkbehind Classic with a 15.5 Briggs and Stratton. It runs great under light load, except it needs about 5 minutes to warm up before you try to cut at full throttle or it will bog down, then start to run rough and throttle-hunt. When there is a heavier load (taller grass) it will start to bog, the governor will kick in, and the engine will start to backfire while the governor hunts. I can see the throttle moving back and forth when this happens. It won't smooth out (even when load is gone) until I manually throttle down for a few seconds. I removed the carb and sprayed carb cleaner in all jets and passages. What's up? Thanks.