Bicycle Mechanics - LX shifter, broke??

My LX shifter will shift up from the 12 to the 21 (up 5), but it will not continue up the other 4 cogs.
There is nothing left in the shifter, it just moves with no resistance, nothing, nadda.
It doesn't matter which chain ring I'm on and the first 5 up shifts are indexing fine.

???

You can remove the shift cable and take a the shifter mech out of the body by removing a few screws. Then you can see the ratchets and see if one of them is sticking or if the spring is broken. If it is sticking you can spray some solvent on it and action it with a pick or small screw driver until it frees up then lube it with light oil. If the spring is broken then it is time for a new shifter.

Hmm, so if the spring is broken the entire shifter is shot? That sucks.
A new RS shifter goes for about $40.
I'll take it apart first and have a look eh?

Thanks

Have you tried spraying chain lube into the shifter? If it's a slugish on the gears where it will work it could be some dried lube inside the shifter.
Have you checked the derailer to be sure it's clearing properly?
I always check everything else first. When I'm sure everything else is aligned and ready to work, THEN I go for the shifter.

As I stated, it works fine from the 12 up to the 21 then there's no input left in the shifter, just air, not sticky, not sluggish.
The derailluer is not hitting anything.
Interestingly though, when I first started getting the bike ready I seem to remember it shifting all the way up to the 34.
So, I will pull the shifter apart and see what happens.

I was just curious to know if anyone has experienced this same thing and what they ended up having to do.

I fix bikes for a living. I have seen this, or similar, many times. That is why I recommended what I did.

Ok, 10-4 will do.
I'll letcha know.