The CO50 front dérailleur is part of Shimano's Tourney line of bicycle components. The front dérailleur is responsible for shifting the chain to each of the bicycle's front sprockets, or "gears". Adjustment of the dérailleur is required if the chain struggles to shift to one or more of the sprockets. Accurate adjustment of the front dérailleur ensures that the dérailleur shifts efficiently and accurately.
Shift the bicycle into the smallest front sprocket. Then shift the bicycle into the smallest rear gear. The particular combination of the two gears positions the chain closest to the inside of the bicycle.
Note the two screws atop the Shimano CO50 front dérailleur. The screw farthest from the bike controls the dérailleur's low range. The screw closest to the bike controls the dérailleur's high range. The range determines how far in either direction the dérailleur is able to pivot.
Use a Phillips screwdriver and turn the low-range screw until the side of the dérailleur is approximately 0.5mm from the side of the chain.
Shift the bicycle into the largest front gear. Then shift the bicycle into the largest rear gear. The particular combination of the two gears positions the chain farthest from the inside of the bicycle.
Use the Phillips screwdriver and turn the high-range screw until the side of the Shimano CO50 dérailleur is 0.5mm from the side of the chain. To check the clearance, grab the dérailleur cable and pull the cable taught -- note the gap between the dérailleur and the chain.
Shift the bicycle into the intermediate front gear.
Note the cable adjusting bolt, where the Shimano CO50 cable enters the gear shifter. Turn the cable adjusting bolt until there is a gap of 0.5mm between the inside of the dérailleur and the chain. An anticlockwise turn decreases the gap. A clockwise turn increases the gap.