Falcon AMC 20T clutch back plate removal

Hi all,
just picked up my granddads old Falcon on the weekend which has stood in a shed for 30 years and planning on getting back on the road.
First job I always start with is removing the engine, but this is where I am becoming familiar with the old British ways of engine assembly; drive sprocket inboard of the clutch???!
Well I've managed to get the clutch basket sliding along its shaft but the chain going to the crank sprocket won't let it slide off until I can remove the sprocket from the crank also. I've tried putting a spanner on the nut on the other side of the engine where the alternator is, but ended up just loosening that nut off. I reassembled the clutch, put it in gear and held the rear brake down and tried undoing nut, but the nut resisted my efforts and the rear wheel slowly started turning. Is there some special tool I need to hold the crank in place so this nut can be removed? All I want to do is remove the engine!

much thanks!

I've made tools in the past for holding clutches out of old clutch plates by welding a bar to the metal plate and making sort of a large spanner to hold the centre and basket but in this case you may be better off buying a clutch holding tool as you may find it hard to find a replacement. They are usually only about £20.00 and look a bit like a weird set of vice grips.

I managed to get myself in by using the back brake and sticking a hammer handle through rear wheel spokes and placing it up against the swingarm. A few minutes alter I nearly had a disastrous incident with the reverse clockwise thread on the sprocket nut, but stopped turning it just in the nick of time!

I am not quiet sure what you trying to do. If its to remove the clutch basket and your saying because the chain is tight you cant pull of the clutch basket. You will have to remove the engine sprocket or split the primary chain. This sprocket nut is not left hand thread. If it all turns put a cut piece of brush pole and jam it in the chain at the clutch end and then try with a spanner.If that seems too tight hit the spanner with a mallet. The only nut that is left hand thread is the gearbox output sprocket under the backplate. If this is tight do as you was saying and put it in a high gear or better still get an impact air gun on it.

Regards Ken