Speed changing is uaually due to what gear yo have it i and the gear ratio changes in the trans ......can`t think of anything due to a belt change ,,,how long did it set up before you changed the belt .....I had one that a buddy of mine had and had to take trans apart and regrease everythin but its fine now .....good luck not unless its keepin the belt so tight it can`t move maybe
bg, November 2005