Stuck Clutch

I've put a rebuilt '78 kz 1000 motor in my '75 Z1 , so far unstarted. ( In the process of building a roller starter). The rear wheel spins freely, but after i've put it in gear and shift it back into neutral there is so much drag it takes a lot of force to break it free and then it'll turn freely again . The clutch plates were new. Got me baffled.
Jerry.

That isn't a clutch problem. It is a tranny problem. Sounds like a shaft bearing. It might go away under power and a little use might free it up.

Thanks. I've had the clutch apart and it looks and works fine. What you say makes sense. I'll let you know how it works out.
Jerry.