Hello, looking through this forum I have found information on the replacement of the front sprocket, but not sure about the allen bolt in the center sprocket shaft, and the square slotted nut as well....I have done the RC51 front sprocket changes on 4 different bikes, and all ran so much better with the front sprocket being replaced with 1 tooth smaller...way less vibrations..(.just geared to tall)...The RC51 does not have the allen or square bolt...just the sprocket, washer, and nut....do I take the allen out first, and if so, what direction to remove...then would be the square shinny slotted nut next, then the main nut that actually holds tight, the sprocket? Again right or left thread...for the square nut and main sprocket nut ?.......any reply's appreciated!......:beatnik: