What people don't understand, is that NONE of these sellers actually produce the engine kits themselves... They buy them ready made & packaged from China.
Most kits don't come from China with any instructions, & the one's that do were written by a Chinese guy who has very little command of the English language (& very little experience installing a engine kit).
Then there's the problem of trying to write quality instructions that will work for literally millions of different style (& size) bicycles... (you can't); The instructions would be bigger than a old phone book!!
Last... The US sellers aren't much better than the Chinese... They're a just bunch of office & warehouse workers (making minimum wage) who don't have any experience installing these engines either... (How's the kid answering phone calls & emails supposed to figure out (over the phone) that your engine isn't mounted level enough to work)????
This is a big part of the reason I stopped selling (& shipping) engine kits years ago... (it's much easier for me to install it myself than to walk someone else through it over the phone).
Anyways... Welcome to the forum, & welcome to our addiction!