Putting the twist lock discussion on hold a bit, read this about breaking in your new genny engine :http://www.mototuneusa.com/break_in_secrets.htm
The high points:
1) Break in with dino oil, not synthetic. Dino oil facilitates wear (see 2 below).
2) Run it under load several times to load up the rings against the wall to create a better fit between rings/wall. Goal is to increase compression and reduce blow by which degrades the cyl wall/piston lubrication effect due heat from blowby. Blowby causes premature oil usage and cyl wall wear.
3) Change you oil after the first few hrs..guess what that silverly sheen is in the oil .......
Cabelas, Amazon and Tractor supply reviewssuggest that for 300 bucks @ Tractor Supply this is a winner . These last 600-1000 hrs before a OH, too expensive to OH, just buy another . If you want 7000 plus hrs before the genny craps out, buy a EU series.