Replacing the roller foot on Cobra 8810 / Pfaff 491?

[andcoffee]

Hi, I have a Cobra 8810, which is a post bed machine with a driven roller foot, and I believe it's a clone of the Pfaff 491.  The one I have came with both a roller foot and a feed wheel that are perfectly smooth.  I'm hoping to replace them with a roller and feed that have texture for grip, but I can't seem to figure out how to remove the roller foot from the drive.  I looked at the manual and wasn't able to find anything, either.  The problem is that I'm replacing the entire driving mechanism (because the new roller is actually a larger diameter), but after taking off the one screw that holds it in place, the drive shaft remains connected.   I don't want to start applying force without knowing what I'm doing. 

Not sure how I ended up with a smooth roller and feed as every other video I've seen has the machine with a textured roller and feed, but here I am, hoping someone here might have some experience.  Thanks.