I think
The losi flywheel should come with it's own collet, the wedge shaped piece that replaces the stock steel one on the engine.
First remove the stock Nova collet and put the losi one on in it's place.... the flywheel should fit perfectly on that one.....
I like to use a tiny flat screwdriver in the gap on the collet and twist slightly and slide it off....make sure the new one is all the way on before putting the flywheel on it. pull the crank out as you slide it on....