Remove the bolt and washer retaining the helical gear.
Set a much longer bolt to the depth of the threads.
Heat the helical gear with a propane torch, but not the crankshaft.
With 2 flat screwdrivers putt a little load on the helical gear.
Give the long bolt a sharp snap with a steel hammer.
Helical gear should come loose.
Do NOT beat on the end of the crankshaft or beat the bolt unmercifully.
Examples from webland: