Hi, I recently bought a Horse model 12088 with a electric start 7hp Briggs. It starts fine and runs ok, idles a little high but boggs and tries to die under a load. I figured since it had set for several years the carb needed cleaning, so I cleaned and kitted the carb, new gas and air cleaner. I set the mixture screws and adjusted them and I still can't get it to run right. She still boggs and tries to die under a load. HELP...thanks..