Antwort auf „I changed the spark plug and it's running worse than before”If in fact changing the spark plug made any difference at all.*Make sure the replacement spark plug is the proper heat range for that particular engine. Should be in the 9s, Exp: xxx9x *Make sure the clearance between the ground electrode is .022-.024in if it is set any bigger the spark plug can miss any smaller and it can fowl. * DO NOT USE A WIRE BRUSH TO CLEAN A SPARK PLUG. it will leave Metallic scratches on the porcelain and cause Premature failure.