Used it a number of times for other purposes inc. the nut you mentioned. Could not shift it. Put the driver on't - seemed finger tight.
Forewarning. Just wait till you come to putting the spring link back in the chain, a nightmare. In the end I think I assembled it by putting the sprocket init then squeezed it back on the drive shaft. Took me hours.
Later I found you can tilt the engine enough without removing the chain to get the head off.
Thank you very much Mr Haynes .