I didn't even start it, in fact it sat in a corner for a week till I could pull the old oil burning B&S off the tiller and test fit the new engine. That's when I noticed it looked nothing like my "new" Chinese diesel. Fins are dirty, oil dipstick hole had jet black oil around it before I even removed the dipstick.
You're not wrong: These are Chinese imports after all and you're at the mercy of Amazon if things go awry. I completely agree with you on the second paragraph. I didn't spend my lunch money on it, though I hope they take it back somehow on the premise it's a used engine disguised as new. If that doesn't work I'm certain it'll be a fine running engine and a testbed to run my used oil in.
To adapt it to my tiller I need to fabricate and weld a new mounting plate-- the engine is bigger than the old B&S, so it needs to be placed a bit further back and to the front. At the end of the day it's a pulley/belt driven tiller, so nothing insurmountable. I haven't had any luck finding a 2-1/2" OD pulley for a 20mm shaft, so I think I'm stuck in the rudimentary mill-the-shaft-down boat like I did with that last one.