https://www.lawnmowerforum.com/member.php/6570-robert-honda
send robert @honda a private message with your questions, he is the Honda go to guy, works for HONDA.
He has not posted on here for over a year.
Welcome fellow Canuck! The valve clearance is .005"-.007" on both. I don't know how to read their serial numbers. I wanted to rebuild one on my HR215 mower but could not source gaskets. GX140 gaskets are readily available, go figure.