Suntour cranks are older cranks for bicycle's that are no longer made. Suntour cranks work with cotterless bottom brackets and are attached to the spindle via an 8-mm set of hex screws. If you are removing the Suntour cranks for upgrades or to service the bicycle's bottom bracket, you'll need to remove the chain before taking the Suntours off the bicycle.
Place the bicycle into a work stand. Turn the pedals and shift the gear so the chain is over the largest chainring and the smallest gear off the sprockets.
Place the chain tool over one link of the chain, and align the tool's pin to the link's pin. Turn the handle clockwise to push the pin out of the link and crack the chain. Remove the chain.
Insert one 8-mm wrench into the Suntour crank on the drivetrain side of the cranks. Insert another at 180 degrees on the other side of the cranks.
Use opposing force with the two wrenches to loosen the 8-mm hex screws on the cranks. Turn the wrenches until the hex screws can be removed by hand, and pull the Suntour cranks off the bicycle.