Only a comment....
Weeks ago, I purchase my first 4-stroke engine a RCV 60. I was a little bit afraid about this 'break ins' and so...
But, surprise, no problems. After 2-Hours break-in, this motor is running and running...great.
It's smoking like a old man with a big cigar.....kidding.
Next, I buy an RCV 90.
Cheers.