There are plenty of motorcycle magazines explaining how to fix this nagging problem.
But keep in mind that the crankshaft pinion shaft runout (the shaft will hop up & down motion) can not exceed 3-thousands of an inch otherwise the gears will not work. If you like to ride hard the runout (unbalancing/misaligning crankshaft webs) can easily creep beyond .003" and the gears will clash causing catastrophic havoc to the engine.
The problem is the gears are "stacked" one upon another instead of side-by-side so if the crankshaft is out of alignment (and it will get out of alignment just with normal wear the crank and camshaft bearings) the gears will "compress together" and that can break the engine cases, bearings, crankshaft, cams and it devastates the engine to near worthlessness.
So, it there is now cure now for the Harley-Davidson Twin-Cam engine.
The engine will fail suddenly and catastrophically and it may even take you down to the pavement as the engine oil coats your rear wheel.