Thanks Neal 16 quid very expensive but needs must eh?Depending on the int dia which one would think is approx. 33/34mm one will want something like this if one can find the correct size, the zoro site has various sizes .
Sealey Motorcycle Swingarm Lock Nut Socket 4-Pin 3| at Zoro
Look for 4 pin lock nut tools or swing arm removal tool.
Tried all that, looks like a normal thread, hope I haven't stuffed up the threads with my hamfisted attempts with a screwdriver and hammerCan you see enough thread in the notches to check left/right handedness?
Heating the chainwheel might help, also tapping gently radially all the way round.
There is one in the Men's Shed (Southbourne Bournemouth) where my friend Vaughan (his wife's bike) and I go on a Wednesday but it is just a couple of millimeters too small-always the way, ain't it.....you need a special 2 pin spanner to remove the silver cup.
Ask Andy for one.