[DaveO430]

Check the trike drive line first, a clutch going out on an 1800 is indeed rare.

 

[DaveO430]

Don't know how the make the driveshaft for the trike but does it maybe have a shear bolt in it? That would explain the bolt head and why it doesn't move. Can you see the front part of the shaft where it connects to the trans to see if it is turning there?

 

[DaveO430]

Thanks guy, both great ideas and after to speaking to a nwing mechanic of nearly thirty years he too seems to think slave cyclinder. .

I am going to stick my neck out here and say no way is it the slave cyl.