Intermittent trouble with rear gear shifting

[imaytag]

Every now and then something strange will happen to my bike. I won't be able to shift up from 3 to 4 on the rear gears for a day or two. I can shift freely between 1 and 3 and if I somehow end up in 4 I can shift freely between 4 and 7. But then if I shift down from 4 to 3 (which I can do no problem) I cannot shift back up from 3 to 4.

Whenever this is going on the lever I press with my thumb does not click like it does when shifting through other gears and the gear indicator either remains on 3 or seems stuck halfway between 3 and 4. The derailleur does not move and it doesn't sound like it's trying to shift (no clicking sound or anything). The cable twitches a little when I press the lever but not as much as it does when shifting through other gears.

As I said the problem is intermittent and it will come and go, seemingly without warning. Does this sound like the kind of problem I might be able to fix myself or should I get it looked at? Any advice would be appreciated!

P.S: It's a couple years old and was cheap to begin with (I think I paid about 250 for it)

[nfmisso]

Sounds like a shifter issue. Trigger shifters and brifters require periodic flushing with solvent and re-lubricating.

Take a look at: http://bikeride.com/rapid-fire-shifters/

[imaytag]

Thanks for the link! My attempts to open up my shifter have been thwarted for now by a badly stripped screw, and while I was tinkering around the problem fixed itself, though no doubt it will appear again in a few days. I'll see what I can do about the stripped screw once the problem reappears. If I run into trouble after that I'll return here.

Thanks again!