Sorry Gordon, I was thinking hub gears since this often crops up with them, and I was forgetting the Emotions! I'm not familar with the size of motor drive sprocket they use.
If you do mean the drive sprocket on the motor unit, changing from a 14 to a 9 seems too drastic since that will slow the cadence drastically, the power coming in only over very slow pedal rotations. Also the top assisted speed would drop from 15 mph to about 9.5 mph, very low. Even the 11 tooth will have quite a lot of those effects, the top assisted speed dropping to below 12 mph.
Changing the rear cassette for one with a larger low gear sprocket but keeping the upper gear sprockets the same will greatly improve the hill climbing without those performance ill effects, so I think that's a better solution.
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