As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOTS REPORT EXCESS MAGNETO DROPS OF GREATER THAN 300 RPM'S AND SEVERE ENGINE ROUGHNESS. THE FLOAT IN THE CARBURETOR WAS REMOVED AND FOUND THAT THE REAR-MOST CHAMBER WAS FILLED WITH FUEL. FLOAT IS A PLASTIC DESIGN WITH 3 VISABLE CHAMBERS. THE CHAMBER THAT WAS FULL OF FUEL WAS THE ONE CLOSEST TO THE NEEDLE VALVE. UPON INSTALLING A SERVICEABLE FLOAT, ENGINE OPERATED NORMALLY.