I was unable to free mine (54 1st 235) with a hammer. It had been rusted fast for I don't know how long. When I had the carb off for a rebuild I blew a lot of air through the manifold and cranked the engime a few times to expell the fumes then hit the manifold and riser shaft with a torch. After a few minutes I got a little wiggle. I removed the heat and just worked it back and forth until I had full travel. I have not lubed it but perhaps I will now that I read the other posts.