On the right hand side of the motor, fit the woodruff key to the end of the crankshaft.

Fit the main helical cut gear adding a little grease or oil on the rubber oil seal. Make sure the woodruff key is not displaced when installing the gear.

Follow this with the oil and water pump drive gear (which has no key)....

and then a washer and finally the retaining nut. To tighten this up, you can lock the crank with a con rod tool, or if the flywheel is already in place, you can use a flywheel holding tool.