Hi guys! I really appreciate all your replies!!
In the meantime, I have mostly taken the engine apart. Here are some pictures and a video:
https://drive.google.com/file/d/1xpNAleiYelhwdK9nygMtbSFYBc4qhB3u/view?usp=sharing...
Thank you all for your response!
I have been able to check out a fair amount in the meantime. The blade is definitely not bent, there are no shiney spots of the blade on the metal cap either. The flywheel is cleaned (bottom + top; there was a lot of grass in between).
The flywheel key is still...
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...
First, this lawn mower did not start at all. I replaced the spark plug, cleaned the carburetor, changed oil and gasoline, cleaned the flywheel (there was grass stuck to it, removed it a bit with a screwdriver) and the engine worked (hooray!).
BUT: the engine now makes a rattling noise. It is...