Tapered Splined Crank Removal and Replacement
Because this type of crank attachment is often part of an integrated crank-bottom bracket set, there may be several variations. The crank has slots around a round opening, but the fitting is tapered so the cap bolt cinches it tight. The slots fit onto teeth that stick out from a hollow round spindle in the bottom bracket. You need a special crank-pulling tool. Often, the tool is specific to the bottom bracket of the bike. If you have the right tool for your bottom bracket, remove the cap and use the crank-puller tool (see below). If you don't don't have the correct tool, here's how to do it in an emergency with a standard crank-pulling tool. Other crank types: standard female-threaded tapered spindle, male-threaded spindle with nut, untapered splined spindle.
If you have the correct crank-pulling tool for the bottom bracket, this is where you use it. If you find yourself making an emergency repair, and your toolbox contains old crank-pulling tools -- none of which fit -- here's the method. It's not sanctioned by any manufacturer, so if you break something, tough patooties.
Find hard washers that are approximately the size of the dowel's diameter, and have holes too small for the crank-pulling tool to slip through.
Turn the center piece of the crank-puller so the "pushing rod" part comes back close to the larger (outward-facing) threads.
Thread your crank-pulling tool into the threads on the inside of the crank.
Leave the crank there. You just need to have a hole where you can see the other end of the dowel.
Here I'm using a long hex wrench to push the dowel.
Now, do the project for which you removed the crank (such as chainring replacement.)
Put the power-side crank back on. If you replaced chainrings, make sure the power-side crank sits over the raised metal position indicator on the large chain-ring. Use the cap bolt to tighten the crank onto the splines.
Replace the cap bolt on the opposite side, if you removed it. The opposite-side crank should be 180-degrees from the power-side crank.