This all boils down to taking responsibility into your own greasy hands. Yes I could go on and on and on and on and on and on like others (and not use any punctuation other than enough commas to put me in a coma) about how bad the chinese stuff is but I won't.
Bottom line is that if you ASSume these engines are without issues then you deserve what you get. But if you take your time and do some very simple blueprinting then you'll be rewarded.
My job is building V-Twin engines (think Harley) and I feel like a combination watchmaker and blacksmith as seldom does anything fit the way you'd expect it (or the way it should). American big twin bikes are nothing like working on cars where you can be pretty sure that stuff will fit right out of the box.
Checking the length of stud ends and the depth of the holes is SOP for me. I chase threads, blow them out with air, wash them with acetone and if using a threadlocker I allow it to set up overnight before applying torque. Yes, I'm the anal version of Felix Unger (you graybeards should get that reference LOL)