Generally the sprockets are changed to get a little more acceleration or fine tune the bike to a particular track. I noticed a big difference when I went 1 tooth lower front sprocket. It pulled so much better off the line. I even had it geared -1 front, +4 back for the 1/4 mile but, ended up going back to stock on the front while +4 back because I had no time to get my feet up to shift to 2nd gear while drag racing. If you haven't don't so already check out the threads on the ecu jumper wire mod as that will really wakr up your bike.
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