Don't feel alone on this one! I did the same thing and had the same results!
I did contact the seller and after a long time we finally had a small compensation.
This does not even come close to down time not to mention the endless hours wrenching the old one out and new one in!
More so like you say, now what, still don't have a ride!
I started calling around again a bit wiser this time I hope because if all goes well will fire this second engine today. A bit wiser but still a crap shoot. There were a few questions I asked that helped me select this engine.
I asked myself how quickly did I want a motor and would this make me compromise possibly waiting for another to show up.
The second &......
Had the seller actually driven or can run this motor.
If so did it smoke or use oil?
Were there any unusual noises?
Were they willing, did or can do a compression check.
Are all the spark plug threads good or are there coils?
What is included in motor purchase. i.e. Carb isolators, Alt., Starter, Oil bypass hose, Clutch.
Are all the cases and covers there and good.
Any broken fins, cracks etc...
This second motor came from Louis, He answered the questions, I did not ask the compression one because he said he had actually riden it "recently" and it ran fine. He told me for what ever reason the owner had done some ugly things with a can of black spray paint. Compression was good and bead blaster took care of paint. I forgot the carb isolator question so it cost me $22 each for new but made life easier them being fresh and flexible to get carb rack on.
If you don't get the answer you want to hear just think of it as another potential "bad" motor or more $$$ and time from you.
Ol-SMOKEY did run pretty good so between it and original will be the Big Bore rebuild project but for now let's hope the one will put me back on the road!
Wish me Luck,