I assume you're talking about the drive pulley for the auger that's your hold-back. Some can be a real bear to get off. I'll expand a little on what's been said adding a thought or two.
Being you didn't mention the model of blower, so here's some general stuff. Typically the pulley has 2 set screws, need to be removed or loosened. Here's where the fun begins. soak the heck out of the shaft, the holes through the pulley etc with penetrating oil. Helps to have an extra hand or two here, couple of prybars between the housing and the back of the pulley hub, a short drift and hammer, put tension on the pulley and rap the end of the shaft via the hammer and drift but be sure to avoid mushrooming the end of the shaft.
If it's really stuck and you've done the penetrating oil, heat etc without success then consider this. In those cases I've used a bearing splitter to pull it off. You will have to drill a couple of holes through the pulley, put the splitter between the pulley and housing, thread in the extensions and then add the top. Now it functions just like a gear puller against the pulley but won't bend the pulley like a regular gear puller would. It may not be pretty but you get the pulley off and being it's low speed, a couple of extra holes it has not hurt on any one I've had to do that on.
When reassembling, add some antiseize to the shaft and pulley in case they ever have to come apart again in the future.