21 INCH 12 speed rear problem

[jacobojajati]

Hi All, I'm new to the forum and need some help with rear "D". My son got a gift of a used 12 speed MTB. the bike as twist gear change. when we got the bike we had going from high to low changing gears on the rear. I cleaned and greased the "D" and oiled it. there was a cable housing that was fried on the top bar i did not change the cable housing because i don't have one readily available but i did the best job i could of cutting the fried housing an sticking it back in its place. He can now shift form first to sixth in a simple soft motion but as soon as he wants to go back to first the gear change gets stuck in 4th and can not go down even with my 200 pound adult hand. i do want to also note the adjusted on the shifter is chipped but id does not seam to affect the shift. I have disconnected the cable from the "D" and the shifter goes back and forth with ease. I have checked the low and high limit bolts and everything is fine. The tension when i move the "D" by hand seams as tight as the other bikes we have at home. I want to fix but have no idea where to start to look.

Any help would be greatly appreciated by an exited 9 year old cycler and his dad (me)

[painkiller]

start with some pictures if you could

[nfmisso]

and your location, maybe one of us is close enough to take a look.

[Joe_W]

Look at the cable routing again. If both the dérailleur and the shifter can move freely (without the cable attached) it should be the cable, the housing or the routing. Can you move the cable easily? Is the routing inside the shifter correct?

Look at http://sheldonbrown.com/cables.html and check the cables. If the housing already was frayed you should probably replace it (and the cable). Housing is inexpensive, maybe 2EUR / m (1USD / ft ? too lazy to do that conversion), tops. Make sure you have the correct cable type (shifter and brake cables are different, as is the housing).