The weighted flywheel is there to help in idle. Remember, this is supposed to be a "trainer" engine, meant to be on planes flown by beginners (i.e. alpha 40 and such). However, it is plenty capable of an engine if you want to put it on another plane.
With the added weight on the crankshaft, the theory is that the inertia will help the engine idle slightly lower, and slightly smoother. This goes along with the low pitch 3 bladed prop that comes with the PTS to help the plane slow down quickly and substantially for landings.

Take the flywheel off, as suggested above, with a socket and hammer. Put the drive hub back on, and you will NOT notice a difference in idle (eg the engine will idle just as dependably as it did before). However, you will notice a difference in spool up time.

Now, the prop. You will need a different spinnerone meant for two bladed props. They are fairly cheap, come in all sizes and colors (but you will need one in the 2.5 to 2.75 inch range), and easy to install. Put on a good 11X6 MAS or APC prop and go fly. You will think it's a new engine, I guaranty you.