Bearings won't fit in that engine.

Look at this picture of the 40 LA crankcase:

http://www2.towerhobbies.com/cgi-bin...?&I=LXCG67&P=Z

... and this one of the 46 FX

http://www2.towerhobbies.com/cgi-bin...?&I=LXCG74&P=Z

See where the bearing go in the 46FX? One at the front of the case, and one between the carb and the
cylinder. No room for bearings in the 40 LA.