RB&MTBJim

I am helping a friend do a costum build on his Ti Lemond roadbike. The one thing I am having trouble with is the Ulterga rear derailleur. It is a new 9speed derailleur and a used 9speed shifter. It shifts fine until it gets to the 4th cog and skips to the 6th cog. Then shifting down it skips from the 4th cog to the 2nt cog. No matter how much I adjust the barrel adjuster I cannot solve the problem. Does anyone have any ideas as to what the problem might be and how to fix it.

Thanx

HillRider

I sounds like it wasn't aligned correctly from the start. Try this:

1) Disconnect the cable and be sure the limit screws on the derailleur are set properly by moving it by hand while you turn the crank. The chain should go from the smallest to the largest cog cleanly with no hang-up or tendency to overshift and spill the chain at either extreme. Adjust either or both limit screws as or if needed.

2) Shift the right side (rear) shifter several times until you are certain it's in the high gear (smallest cog) position. Pull on the cable as you do this to be sure the ratchet goes to the highest gear position.

3) Turn the barrel adjusters on the derailleur and on the frame's cable anchors all the way in then out one turn each. Turn the crank to get the chain on the smallest cog.

4)Pull the cable snug and reattach it to the rear derailleur's clamp screw.

5) Turn the crank and try shifting one click from the smallest cog to the next small cog. If the shift is clean, try the rest of shifts both ways. Use the barrel adjusters as needed to get the first shift clean both up and down. The rest of the shifts should then work properly unless there is something wrong with the shifter.

Retro Grouch 

Check the derailleur hanger alignment. As cassette cog spacing gets closer as it is on 9 and 10-speed cassettes, the shifting becomes progressively more particular regarding hanger alignment.

Steev

It could be a frayed cable catching as it passes over some particular place, the entry of a cable housing for example. Another cable problem would be gunked up housing or corroded cable. Check the cable is good and able to move freely.
Another possibility is a bit of gunk or dried greased in the pawls and ratchets of the shifter. Where did you get it and why was taken from its old use? Maybe you've found the reason. Flushing with solvent and a re-lube should help if that's the issue.

Bobby Lex

+1. Whenever turning the barrel adjuster doesn't fix the problem it's best to back to "square-one" as advised above. (Assuming the problem isn't a worn chain or cassette).

Bob