Why does the freewheel down shift lever on my mountain bike have no tension when moving to lower gears?

When I go to push on the down shift lever it moves all the way forward without changing gears. Sometimes it'll catch and change gears at the very, very end of the ';travel'; of the lever, but usually not. This only seems to occur going down from from the 4th sprocket; from 4-5-6-7 I can shift with little or no trouble. I'm just starting to learn how to maintain my bike instead of taking it in, so thanks for the help!Why does the freewheel down shift lever on my mountain bike have no tension when moving to lower gears?
Your cable is frayed or kinked.



If the cable is kinked, reroute it so that it has the fewest number of bends as it approaches the derailleur. If that doesn't work, replace the cable AND housing.



Since you are just starting out in repairing your own bike (congratulations!) make sure that the bike is shifted into high gear (smallest sprocket in back) with the lever to match. Reroute the cable and housing and readjust.



**There is NO NEED to touch the 'H' and 'L' screws on the derailleur when replacing the cable.**Why does the freewheel down shift lever on my mountain bike have no tension when moving to lower gears?
This shouldn't be the best answer. I followed and voted for Joel's advice below, which solved my problem in about 30 sec.



Zack

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It seems some users have more interest in gaining quick points than actually reading the query correctly.



With trigger or STI shifters the small pawl/spring mechanisms which release cable (shift to lower gears on the rear) can become congealed with dirt and old grease. This means that the thumb shifter (on mountain bikes) doesn't seem to ';catch'; to reel in the cable, and pushes all the way through the movement without resistance.



The way to solve this is to flush out the shifter with a spray lubricant like Inox or a teflon lube, while working the shifter. This will get rid of the old grease and the dirt which is impeding the shifting mechanism.
I'm assuming you mean that when you try to shift into a harder gear, it's hesitating or not shifting. (It depends on your shifters and derailleur as far as what gear ';1'; and gear ';7'; mean...) The info below is for this problem. If you're actually having problems shifting to an easier gear, then you just need a simple cable tension adjustment. check out the ';repair help'; section at www.parktool.com for great instructions and photos on derailleur adjustments and setup.



So....not shifting into a harder gear:



More often than not, it's grit and grime that causes this....it could be a damaged cable/housing like Mirage said, but before you go replacing that, see if you can clean things up and use a little lube. Dribble a light lube into the cable housings (or remove the cable and lightly grease it). Remove the chain and work the derailleur by hand, then use a degreaser or WD40 to wash away any sand/dirt/grime in the pivots....then lube them with some chain lube or another light oil. Most of the time this is all you need to do, but cables and housing do wear out or rust, so if the cleaning doesn't help, pick up a new cable set. Also, carefully check the routing to be sure that it isn't binding or kinking anywhere.



A last resort....sometimes on cheaper shifters the springs aren't very strong and the grease can dry up. If none of the above steps help, remove the cover plate on the shifter and spray a little WD40 or silicone lube on the ratcheting mechanism. Don't try to take it apart or adjust anything, just wet the grease with lube. This seems to be a common problem on Shimano Deore and lower level shifters. The higher quality ones don't seem to be affected by this.
Get new housing and inner cable.