Seeing how it used to work, I'm not sure shimming (i.e. purchasing a shim-kit, etc.) isn't a band-aid solution. When you install your flywheel, you must make sure the tapered cone is all the way back on the crankshaft, then install the flywheel and the nut. You need to pull on the end of the crank (away from the engine) when you slide the cone and then the flywheel on. If you don't, the flywheel can tighten against the cone with a small space behind the cone. This space is needed up front for your CB to spin freely.