My Crastman Platinum lawn mower is making a loud clanking sound.

Recently, my Craftsman self-propelled Platinum mower is making a "rattling/clanking" sound. There is now vibration at all and the blade is tight. I did use gasoline that has 15% ethanol in it. I just switched to a better premium gas. Will this clear up? I ran about 6 times cutting my lawn at about 45 minutes each time.

Things to check, bent blade, oil level, tight blade in the proper position with the blade adapter. If all these are good, post back with the model and serial numbers for both the engine and mower. We need to know what you are talking about.

A deck belt with a chunk missing or a bad pulley could also be the cause if the noise is from deck vibration.