Replace the 14:9 with a 14:10 at least, that will give you more than 20mph out of the bike at least. Finding a 14:9 is difficult and will be more $ than a 14:10, 14:12, 14;14 or a 15:15 because it is an unpopular size because it is used as a restriction for mopeds to keep them at 20mph rating.
Just saying