see what you started with one little word? if someone called my bike "junk," man, it's on.
by the way, where exactly is your bike and all it's parts made?
if you want a "non chinese junk engine," then you need to build a time machine first.
with all that said, and back to your questions, the engine choices are very limited if you don't want to go the 2 or 4 stroke china route.
as Joe said, try a morini.