I have a YS fz 63 that had an issue and it was replaced no questions asked. both engines (ran) run great. you have to set it up properly and break it in properly or you will have problems. nothing you cant figure out if you take the time. Saito 4 strokes are also noted for being tough to get set up right, so it just depends on if you are a "ford" man or a "chevy" man. I have both engine types and I have more problems with the Satio than the YS. I would buy another YS motor when I need one. like anything you buy now days that is produced in great numbers "lemons" do get by QC, just like "Fords" and "chevys" . Ultimately it depends on what you are comfortable with and how much tinkering with the motors you are willing to deal with. As far as parts go, when I need one it was available. hope this helps.