Small Engines (Lawn Mowers, etc.): Husqvarna Model 55R21HV Vibration Problem, vibration problem, lawnmower

Question
I have a Husqvarna Model 55R21HV lawnmower, and although I've maintained it well (replaced spark plug, relaced filter, changed oil) it's vibrating badly.  Might this be due to some blade problem?  Can you provide information about how I can fix the problem, please.

Answer
yes it could be your blades one is to take your blades off to get new ones or look in your owners manual that will have a part number for your blades next thing before you do that make sure your motor bolts are tight that bolt the engine down to the tractor let me know how you make out thanks