My chain derailed and proceeded to jam in the engines cog after skipping a link. The chain is seated on the cog but it's doubled up inside the covered area. I cant seem to feed the chain through in either direction or can i figure out a way to fix it with out taking a grinder and cutting out the links. Is there any other way to fixing this situation? Can the cog pull out of the housing so i can move the chain? Also, whats the easiest way to align the chain from the rear wheel to the engine?