yeah their do, cheers. i was browsing through the gallery and some has 1 on their its what made me ask really, its on the first page of the bike pics. i did see a raven 4.0 but its a right bodge lol. the guy uses a rear mech as a single speed converter and the chain must only be clearing the ground by about 4-5 inches were it goes round the jockey wheel. look on ebay at that i reccomend