Well, I bought the bike used, and have been happy with it, but thought I should swap out the chain and sprokets. I am having a hell of a time trying ro remove the front sprocket. What is the trick? Is it reverse thread? do I put something inside of the little hole to keep it from turning? I do not watch to wedge a prybar against the case to keep it from turning for fear I would crack it. Any wisdom oh wise fellow TTers?