How to fix this sound - Briggs 500e series engine lawn mower

[kjonxx]

Is it possible the blade adapter is loose?

 

[slomo]

Not if the blade bolt is tight. All that should tighten when you overtorque the blade bolt with your impact gun. Bolt only needs a rough value of 35 ft lbs.

 

[kjonxx]

Not if the blade bolt is tight. All that should tighten when you overtorque the blade bolt with your impact gun. Bolt only needs a rough value of 35 ft lbs.

Blade bolt can be tight but if keyway is worn the blade can still rock, I have seen it.

 

[Auto Doc's]

Thanks man!
It could be the cheap recoil mechanism, but it doesn't look like that's the problem. Maybe I can put some WD-40 on some points there (on the white plastic bits under the hood) to see what happens? I'm definitely going to check on rod knock, but I'm still waiting for the delivery of my brand new socket wrench set to access the inside of the engine.
Just wondering: I can move the flywheel/fan back and forth and up and down a bit; is this normal? Here's a video of it:

https://drive.google.com/file/d/1t6cQz3CY6gxFN3_opFIGc0VhWrfLAl1X/view?usp=sharing

Thanks for helping me!

That appears to be a worn-out crank journal in the top of the block. This thing has been run a long time with a lack of oil. The crank should NOT move up and down or side to side like you show in the video.

One (long shot) exception that I can think of is if someone has replaced the oil sump gasket with thicker material than the stock gasket. DIY types can be creative.... LOL

Other than that, there is no (economical) rebuilding to correct this kind of damage.