(if it works) click on my link, then click on photo to enlarge the photo,,
rather rust or not there is debris in that engine, before taking it completely apart I would remove Back Plate, Carb and head and soak it in hot antifeeze, every 2 hours turn the crank, when done clean off the antifreeze with WD, then rinse with rubbing alcohol, once dried add a few drops of oil and turn it over, go from there
just my $0.02 than may be worth $40
https://cimg3.ibsrv.net/gimg/www.rcu...6ef516331d.jpg
Jim