How to Successfully Remove the Crank Arm from Your Mountain Bike
To remove a crank arm from a mountain bike, first, remove the dust cap from the center of the crank, then remove the bolt holding the crank arm in place using a crank puller tool. Then, thread the puller tool into the crank arm and tighten it, which will push the arm off the spindle. Finally, remove the crank arm and repeat the process on the other side if necessary.