hye there it sounds like your pawls inside your hub assembly are not springing out ,these are little teeth that are held in with a spring so they open and close and make a clicking sound sound when you freewheel,ie :wheel you role without pedalling, you need to free these,or it might be that your spring has broken,if its a freewheel that you have which you screw onto the rear wheel,you can apply oil from behind it and the front and let it soak in,if this fails you can actually open it up.
gus
December 2009
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