Crank gear not seated.

I would not ever use anything to tap or hammer it in place. The thrust bearing has to take the hammering load and you don't want to damage that and have other issues; the thrust faces are soft. Use a 3/4"x16TPI bolt to draw it down; get a 1.5" and a 2" bolt and you can use it on the damper too. A big washer under the bolt head pushing on a short piece of pipe as Bob mentions will push the sprocket on.

Also, use some fine wetordry sandpaper or crocous cloth to smooth the crank snout and that will help.