You could always buy a front cog from ebay or better still a bike shop. I cant remember which way around it is but either one extra tooth or one less will give you about 10-15mph top end but you´ll lose acceleration. Other way around you´ll get plenty of pull but lose top speed. A little heads up for anyone who wants a better sound....drill 3 holes in the pipe that joins both end pipes....fill them with exhaust putty before mot time though or it will fail.