Grumpy, I seem to have misrepresented the 'pin'. If you have a look at the second pic ( IMG 1095.jpg ) you can see a bolt on the engine side of the drive shaft near the clutch that has no head. This is the one I am unsure about. Does this hold the engine shaft to the drive shaft and require removing before I can get the engine off???
stu45,
If you undo the nut until it is flush with the bolt end and then tap it on the end it will release from the crankshaft. The bolt shaft is half moon so when you tighten the nut up it locks onto the engine shaft.
Note the bolt does not come out until you remove the clutch housing from the engine shaft.
If you download the parts list from the parts list and manuals area you will see what I am talking about.