Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
Model of engine? Does it have electronic ignition or points and condenser? If you run cylinder check, by removing one spark plug wire at a time, is it firing on both cylinders?
Is battery voltage to the coil constant, or could it be dropping? I'm thinking that coil is breaking down and spark becomes erratic. Service manual link above.