Does it have all its rope on the pulley? If it's been shortened - the circle it turns on is smaller, has less leverage and pulls a lot harder.
Sometimes the pull handles break off and the rope becomes shorter. I just got a saw for free that the owner was going to throw out because it pulled too hard. It's problem was just a short rope.
I have a 55 Rancher for an "el cheapo" saw. It pulls easy as compared to a Poulan Pro. I also have a "yard-sale" 455 I got for $50 and it does have a compression release which certainly makes it pull easier. The 455 is a plastic "homeowner" saw like the 55 Rancher so I assume the 55 would accept a compression release IF the jug is drilled for it. I never felt the need so I never checked.