On the drilled sprocket, clamp the cranks in a vice, find two bolts and put them in opposite holes on the sprocket. Get some form of bar and put it between the bolts and turn. I'm pretty sure theres a guide to it somewhere, I'll have a look and edit in a second On the other one, Clamp the crank in a vice again and grab a hollow bar, maybe 1ft or so. Put a chain round the sprocket and through the bar. Join the chain at the end of the bars and put a Bolt through the chain to stop it coming of the bar, chain needs to be pretty tight. Once it's on, when you turn the bar the sprocket should start to come loose Edit: http://www.trials-forum.co.uk/forum/index....c=108399&hl= Follow that for the 1st one After re-reading the second one it may not make sense, Pm me if you need it explaining better :$