Paul, I've never worked on one myself, but from other threads I understand you need to slide the other half of the clutch off the end of the crankshaft, so the clutch is treated as a single piece. Then you can slide the shaft and clutch to the left far enough axially to move the clutch forward far enough to go past the engine, so it can slide to the right. In other words, take the whole clutch and shaft off together.
To remove the clutch from the crankshaft, look for a cotter pin nut. Undo it two or three mm and tap the nut end of the pin gently once with a mallet. The cotter pin is a captive type - it does not come out, in either direction, but it unclamps the shaft when you tap it. It will then have slight movement axially, showing it is loose. The clutch may be stuck on the crankshaft by corrosion. If so, tap it axially on opposite sides with a mallet and/or carefully use a lever between the clutch and the engine. Be gentle - the engine, especially, is fairly thin cast aluminium.
