Assuming it’s a twin cylinder engine. Check your ignition coils. It sounds like one died and it’s only running on one cylinder. Using insulated tools(pliers) and gloves, while engine is running, pull one spark plug boot off of the spark plug, if it dies that was the good coil. If nothing changes then that’s the dead coil. Another sign of a bad coil is a strong fuel smell since it’s not getting burned.
Answers & Comments
Could be ignition module as suggested. As a test try reducing plug gap to .022 and see if any significant improvement.
Or plugs were installed without gapping and are .044
Could also be one side of carb has fouled.
Assuming it’s a twin cylinder engine. Check your ignition coils. It sounds like one died and it’s only running on one cylinder. Using insulated tools(pliers) and gloves, while engine is running, pull one spark plug boot off of the spark plug, if it dies that was the good coil. If nothing changes then that’s the dead coil. Another sign of a bad coil is a strong fuel smell since it’s not getting burned.