It will fit fairly easily with a shift kit. I have read some people have used as small as a 17". I have built 2 using 21" GT LTS, one of them aluminum LTS with a china girl and shift kit and the other a cromo LTS with a KTM and shift kit. Heres my build link for the KTM....... http://motorbicycling.com/showthread.php?t=46976