If you don't have the correct tool or a spare socket set piece to cut up, a thick walled hollow bar is all you need.
The correct size strong metal pipe is the key.
I found the best is an old CX500 fork!
I took a Zip tie or plastic strip the same width as the cut outs on the clutch nut, held it both ways over the end of the fork & marked the places to cut.
Used a hacksaw to cut down & then turned the pipe on it's side & cut across til the downward cuts were met & used a large adjustable wrench to snap of the unwanted pieces. I filed it all to fit & drilled a whole straight through the other end to put a bar through to turn it with.
You can do this with any bar but if it's not strong enough the tabs will bend. If it's too big you will have to bend the tabs inwards & in doing so you weaken them - see above!
Don't just cut two tabs as the haynes manual says cos that isn't strong enough either.
Give it a go but do it right & strong or you'll have to make a few!
Also, for retightening i found an old fasioned box spanner / plug spanner whose other end fitted inside the fork so my turning bar ran through the wholes on both as a locking pin.
I was then able to fit my torque wrench via the correct sized socket piece onto the end of the plug spanner & bingo - one torqued clutch nut!
I was quite pleased with myself for that one
Hope that's helpfull to someone out there!

