Drive
Two gearbox sprocket sizes are available 14 & 15t. The larger one is recommended to ease chain wear. DID chain recommended. Rear sprocket sizes vary from 36 to 41. The lower size gives a higher cruising speed for less revs but reduces acceleration and pickup. 41 size enables engines to rev out in top but makes high speed cruising less relaxed. Gearbox failures on early models were quite common due to cogs breaking and dogs rounding off. Excessive rear cush drive play can be eased by inserting slips of inner tube rubber between cush housing and rubber spider. Mounting bolts on sprocket can be subject to loosening and also shearing off. High tensile UNF bolt conversion has been done successfully by MOCATI of Bath.