Three-speed bicycles, are know for their ease of use, reliability and ride quality. Unfortunately, without a general knowledge of the workings of a three-speed hub, replacing a flat tire on the rear wheel of these bicycles can be very difficult.
Disconnect the shifter cable. Use a 10 mm wrench to loosen the shifter cable locknut (found near the adjuster at the rear of the bike) slightly. Unscrew the shifter cable adjuster until it comes free from the shifter chain, and move it out of your way.
Disconnect the coaster brake mount. Use a screwdriver to remove the mounting screw that holds it in place. Set the screw aside so as not to lose it.
Loosen the axle bolts with a 15 mm wrench, and pull the wheel out of the dropouts. You do not have to remove these bolts completely.
Remove the tire from the rim and the tube from the tire if it is stuck inside. You may want to check the inside of the tire by running a hand or rag through it to make sure the object that caused the flat isn’t still lodged in the tire.
Put one bead of the tire on the rim. Be sure to make note of any markers of rotation direction.
Put the stem of the new tube through the valve hole in the rim and mount the remaining side of the tire. Inflate with a bicycle pump or CO2 cartridge.
Put the wheel back into the dropouts, set the chain in place and tighten the 15 mm axle bolts. Make sure the chain is tight, or it may fall off while riding.
Replace the coaster brake mount screw on the left side of the bicycle.
Replace the shifter cable by twisting the adjuster onto the shifter chain until it reaches the 10 mm locknut. Tighten the locknut against the adjuster, and make sure the bicycle shifts the way it should.