Rear Derailleur troubleshooting?

Question

My son's bike will not put the chain up on the first gear. The selector will show first, but the chain will stay on the second gear. If the selector is held all the way back, it will start to move up. When released, the chain will fall back to the second sprocket. Is this an issue with a limit screw or cable tightness(or both)?

Answer 1

This is an easy fix...

1) Shift the bike to the cable "full slack" (high gear) position.
2) Loosen the cable fixing bolt on the derailleur.
3) Pull the cable through until the slack is gone.
4) Retighten cable fixing bolt. BE CAREFUL.. don't tighten it too much or you'll break it off.

Answer 2

If the limit screw was adjusted properly to begin with, do not touch it...limit screws do not go out of adjustment on their own. Most likely it is a problem with cable tension. If there is a barrel adjuster on the derailleur, turn it counter clockwise, one click at a time...checking for compliance with each click. Once the chain goes up with a click of the shifter and doesn't fall down on its own, there is enough tension. Another possibility to check (if the cable tension trick does not work) is derailleur hanger alignment. This is best done by a qualified bike mechanic. A misaligned derailleur hanger will cause shifting problems, usually in the upper gears. If your son lays his bike down on the drive (right) side frequently, he may have bent the hanger. Hope this helps!