They seem nice until you look inside.
Plastic cam gears.
Blocks love to crack.
They’re just junk IMO. some are going to last 1,000 hours, some make it to 1/10 that.
Inverse is true for a good engine. Some lemon somewhere slips through.
Really it boils down to they are built as cheaply as possible and they simply dont take the hard work the way a vanguard or Oppy will or a cast iron K341.