What happens when one tooth is added or taken away on a sprocket of a motorcycle front and back?

If its a road bike, chances are its geared exactly correctly to match power with top speed.

Essentially if you add teeth to the rear wheel sprocket, you will shorten the gearing and the engine will hit top revs in top gear before the bike reaches top speed.

If you add teeth to the engine sprocket, the opposite effect, less torque in Top Gear leaving the bike short on top speed.