Mountain Biking - Is it normal?

Is it normal for your chain to click and skip? I do not think it is yet the manager of my LBS says it is. He said that it is normal chain noise. I don't think it is normal. I have tryed tuning it about 10 times now and I can't get the click out of it. I have to wait two weeks for a new shifter and I just reinstalled my old one. I don't know why it clicks. But here is the weird thing I get it tuned perfectly and then it starts clicking again. Also, I tune it upside down. Could my chain tension be too tight? This rear derauiller has been giving me hell for about two weeks now. Could someone please tell me what to do? I really need some help. It skips on pretty much every gear. and it is not the sound of the chain I think it is missaligned but it looks berfect please help I gotta fix this.

I had the same problem with my trek 4300 that I bought used...I replaced the derailure and that didnt fix it...turns out the cassette was worn out because the guy who rode it before me apparently got a lot of use out of it before he sold it....wound up replacing the cassette aswell and the chain (because everyone says when you replace the cassette you have to replace the chain) and it runs smooth an quiet now. I think if you replace your chain and cassette everything will be fine. You can also find some pretty good cassettes for a reasonable price if you shop around.

Funny thing. Not a week after I replaced the chain, derailure and, cassette, my cranks started to work loose and I had to replace those too. So essentially I have put an entirely new drive system on this bike. It was worth it though because I got the bike for $120 anyway and even the parts and labor I have put into it dont equal what a new mtn bike of similar quality would cost.

Thanks for the help. It actually turns out for me that my derauiller was totally misaligned. I set ip my own stant, it wa so ghetto. I used a 2by4 and 2 buckets and a towel on top ow the 2by4 it looked like this
/ - -/ /=bucket
/ / -=2by4 I fixed it by putting it on the stand and tigntening my cable and adjusting the limit screws, also the chain was way too tight. Thanks

If your bike shop guy said that it was normal I'd be looking for a new shop.