The generator is easily lifted up to tighten the belt just right with the left hand and a large adjustable wrench handle wedged between the front of the generator and the intake manifold right next to the generator vertical bracket thus:
You just push down on the end of the wrench with your left hand which lifts the generator up to position as you tighten the bolt securing the generator with your right hand.
That's the hard part. The fan is easily lifted up to tension the belt with your left hand without any leverage while tightening one of its two bolts with your right hand which secures it in place so you can let go of the fan then tighten the other bolt.