I just had the front lens elements off my 'bay Canonet this weekend. My aperture varies as I adjust the ring. As long as it is not set to A, you should be able to move the aperture. While I was degreasing the shutter, however, I noticed that the aperture was not changing.
The aperture mechanism uses very light forces and just the excess naphtha that had found its way between the blades was enough to prevent the aperture from moving. As soon as it evaporated ( an hour in the sun), the aperture blades moved freely.
Mine's a Hong Kong Canonet and the front lens elements removed as a single assembly (though it initially took quite a bit of force to turn the threads, which were gummed up with something, probably lubricant). When I got it off, exposing the aperture and shutter blades, I could see the retaining rings for the front and rear elements had drops of sealant on them. It's not really that hard to get the front lens assembly out, and a good cleaning of the blades couldn't hurt. My shutter and aperture work fine now.
Unfortunately, the front lens element has a good deal of scratching on it and the rear element shows tendrils of mold. So it's now a candidate for resale to someone who has a bad body with good lens elements.