Absolute garbage.---Send it back.---Get your money back.----Now you know why it is some times called ----FLEA-BAY !!
Any pictures of pistons taken through the missing bypass cover.------Maybe one of the motors run on the infamous 100:1 mix.----Despite what some will say the 100:1 mix just does not make for a long lived motor !!----If you can feel the vertical scratches with finger nails it needs boring and O/S pistons and rings.
Where are you located. Why are you not rebuilding your own powerhead?
If rod bearings are bad then likely you need a crankshaft and 2 rods.------Now that gets pricey.----I would want / get 5 parts motors for the price of those items.
Post pictures of rod and the crankshaft surface.