Clubman Cafe racer Mod

[glenn_nirwan]

hi all, my name is Glenn Nirwan.
im only 19 years old, im thinking about getting my first bike.
so i need help with getting to know some engine.

first of all, i wanna build a clubman cafe racer bike (road legal but).
im thinking to put a 250cc engine, my question is,

What is the best 250cc engine i can use for my first bike project with the criteria of reliable, cheap and lots of power?
in my mind right now there are crf250x orcrf250r. but they are not reliable for a long distance traveling right?

please help me out,
cheers

Glenn