Remove the crank arm bolt. Thread the crank puller tool into the crank arm in place of the crank arm bolt. Thread the tool into the crank arm several threads. It may be necessary to use a wrench to tighten further. Now that you have this part of the tool threaded into the crank arm, turn the handle on the tool. As you continue to turn the handle of the tool, this pulls the crank arm off the bottom bracket shaft.
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