adamfoul

Hi, I’d like to start by saying I’m pretty new to road bikes, but have used a MTB for commuting, and I’m used to doing the basics such as cable changes, indexing and adjustment.
I’ve recently picked up a 2nd hand Specialized Allez sport, I think the 2011 version. I decided switch the shifters from the sora 3400 to 3500, as I didn’t like the thumb levers. Grabbed some 3500 shifters off eBay, and I’m having trouble with the front shifting.
Going up, it clicks once and the mech moves a little to the right, but not changing the gear, if I push it in again, the mech moves enough to shift into the top ring, but there is no click, and letting go of the lever the mech moves back again and it drops into the lower ring. I’m confident it’s not too much cable tension, as it won’t ‘click’ even with very low, or no tension at all on the cable.
Is there something I’m missing? Or is it likely a problem with the shifter itself?
Any help much appreciated.
ps tried to add videos, but I’m not allowed to post links. Anyway I could embed them or something? Been a while since I did any sort of code work.

em_525

Make sure the cable is fully seated in the shifter in the shifter's default position. From there, check your derailleur limit screws and be sure that the derailleur can travel enough to comfortably shift to the large ring but not allow an over shift. It's possible, based off what you're describing, the derailleur can potentially just barely shift but that there isn't enough travel.

mattleegee

I would say limit screw as well if you cannot make it into the top ring
Is this problem the same in all cogs on cassette?

adamfoul

I don’t think it’s an issue with the derailleur or limit screws, as I can manually manipulate the mech enough to make it shift, and it was working fine with the old brifters, they are all that’s changed.
Yes, the problem is the same whichever cassette ring I’m on.
I think now after playing with cable tension most of the day, it’s probably the shifter that’s faulty, whatever I do, I can make the shift by holding in the lever, but it never clicks in and holds its place. The right side works fine, and I’ve just put the old one back on and got it working no problem.

Baboo

Where they used shifters. If so they may be gummed up with hardened grease.

adamfoul

Yeah, they are used, a bit scuffed, but they guy had them listed as fully functioning. Think I might be able clean it up somehow?

Baboo

Sometimes you can flood them with wd40 and work them around until the pawls free up then lube them-up. I’m not a bike mechanic but I have had this problem a couple of times. There will probably be others who also have suggestions.

Retro Grouch 

Try backing off your high limit screw about 1/8 turn. My bet is that'll fix it.

Wilfred Laurier

I don't know about the specifics of your front derailleur, but your description sounds like it might be a mis-routed cable. Some derailleurs need the cable to run over a tab - usually a tab built into the washer under the cable fixing bolt - to route the cable further from the pivot point. If the cable runs under this tab, the lever arm is too short and the derailleur will move too far with each click, and the tension in the cable will be excessive, which might also affect the functioning of the shifter.

As for the possibility that the shift lever is faulty, if it pulls cable and clicks into place and releases cable with a click when the smaller lever is pushed then it is almost definitely not the shifter. Faulty Shimano shifters usually don't give a click in one direction or the other. Of course there is nothing stopping you from flushing the shifter innards with WD40 or a degreaser, I doubt it will make much difference.