RD brifter sticks when upshifting
 

Just got a used bike, trying to get some kinks worked out. One of the issues is with the RD brifter (Ultegra 9speed). After downshifting, it won't smoothly upshift: pushing the upshift lever results in both levers moving. A bit of fiddling will set it loose and allow me to upshift; further upshifting is fine until after I downshift again.
Figured I'd ask for advice here before trying to take things apart and messing them up further ;)

It's an older bike and it's winter, both factors that can caused dried out or stiff lube. The problem might be in the cable housing or within the shifter mechanism, or both.

Start with the easier approach, and flush the lever unit with WD-40 or similar, allow to dry overnight or blow dry with a hair drier, then re-lube with a light oil. If that solves it you're done, if not field strip the cable (have a replacement inner wire handy in case yours frays), flush the housing and lube with a light oil or tri-flow. Re-attach and you should be good to go.

Yep, a lot of time dirt and oil gets gunked up in the shifter mechanism, causing the pauls to get stuck and not engage properly. Like FBinNY suggested, use a light degreaser and go to town on the shifter. Completely saturate it, and then let it sit for a while. Let dry, and re-lubricate with a spray oil.

Thanks - I'll give that a try. I don't think it's in the cables, really feels like a mechanical glitsch in the brifter itself. I may wind up having to disassemble anyway, but I have a tendency to make things worse when I do that :p

FYI- Shimano shifters aren't user friendly about dis-assembly. I'd go slow, maybe remove the cover to make flushing easier, but no more than that.

Then don't try. It's almost a watchmaker's job.

I appreciate the warning!