First welcome to the forum. Surging like that indicates clogged jets and passages in the carb. Clean the carb, really well. That will should take care of the problem.
Briggs and Stratton offers up a good trouble shooting guide for their carbs.
http://www.briggsandstratton.com/en...n_troubleshooting_detail_reference_guide.ashx
Briggs and Stratton offers up a good trouble shooting guide for their carbs.
http://www.briggsandstratton.com/en...n_troubleshooting_detail_reference_guide.ashx