Got an '03 husqvarna 55 rancher that is in mostly good shape but needs a ring. I have taken the head off on a couple of these before with no problems but the allen head bolts holding the cylinder down on this one will not budge!! I have rounded 3 allen wrenches, applied heat, and starting to round one of the bolt heads now. I do not think the head has ever been removed and is in factory installed condition. Anyone with experience here have any ideas?