Could you post a pic? I once had a 21cc engine that really didn't look like the other Echo/Kioritz engines, but it was and I decided it wasn't worth converting. I eventually used the cylinder & piston as a "big bore kit" for my Kioritz 16cc. (Don't go there either, as it worked out well but was a very involved project.)

Anyway, the one I had, had a small lightweight crankcase that looked attractive, (light), but it only had one bearing in the crankcase and the other crank bearing was mounted with bend over tabs in a piece of aluminum that was part of the weedeater mechanism and overall metal that I needed to cut off. I could have machined the crankcase for another bearing, but it just wasn't worth it for a 21cc engine.

Good luck,
AV8TOR