Is that a Mugen clutch bell or a Losi clutch bell? If it is a Losi then you do have the wrong bearing. In any case how close is your flywheel to the engine block? More often then not it is the brass bushing that is the problem and it needs to be filed down unless your flywheel is already touching the block or really close, in this case you have the wrong clutch bell, a Losi clutch bell is not meant for a Mugen flywheel and set up, they do fit but the flywheel is different causing the same problem you are having. There are usually only 2 causes for the problem you have

1. wrong clutch bell for flywheel

2. Brass bushing is too long for your engine resulting in your flywheel being too far out thus not being able to tighten it up.