coming from a machining background (worked with machinists and done a course on it my self) it would be astronomically expensive to got a new sprocket machined or altered.
motorbike bits are a good proposition but as has been said chain pitches are a problem. also mounting would be a issue. i haven't had a chance to ask about bits and pieces but will give my guy a ring after Christmas for you.
ide also look on ebay and see if you can find a block from north queens land. i think he was from beelbird park. possibly named tim but he use to have many of these machines to wreck.
