Hi John & welcome to the group. I believe these have a clutch with a friction plate & it has probably all rusted together. You need to strip it without damaging the components if possible. I have never worked on one of these, but assume it may have an asbestos clutch plate that won't want to be soaked in wd40 if you want to re-use it. I am sure one of the other members will be able to give you more detailed advice, but a couple of photos will be useful if you can.