CBX250RS-E Engine Rebuild 25/10/2010

So while I wait for David Silver to tell me whether I'm looking at buying the right tool or not, I decided to have a go at locking up the gearbox and undoing the big clutch centre nut. I filed out the holes in some angle iron so I could bolt it on, weighed down the end of the iron with a toolbox, had a go at undoing the nut and..

Along with 2 stripped sprocket holding bolts and a centre nut that's as tight as ever. Could've gone better, if I'm honest.. The real problem with this is that the sprocket doesn't sit right on the end of the output shaft, so the shaft pokes through it meaning you cannot bolt the angle iron/bar/whatever right up to the sprocket, there's always a gap. You also wouldn't be any better off with a thicker bar, the bolts would be the first to give in. I'd love to be able to change it into a higher gear, but I couldn't get it to change to save my life... Is there a certain trick to this?

Unfortunately it seems fine thread M20 bolts are difficult to find, so it appears a proper tool is in order as it won't cost much more.. Possibly two proper tools are in order though if I can't find a way to lock up this clutch.