I am new to biking and know very little. Pretty fair mechanic, have been rebuilding/retoring old 70's era two stroke street bikes for a hobby, but I am needing some advice on how to troubleshoot my FD. Shimano 105 FD, Ultegra Shifters and RD.
RD works flawlessly.
The puzzle is this:
With the bike in High Gear on the FD, when I downshift to the middle ring, it is usually a very smooth shift. If I then try to shift to low gear, sometimes it shifts, but most times nothing happens, it stays on the middle ring. Then, sometimes as much as a half mile later, it suddenly drops onto low gear. By that time, I have completely passed the need for low gear, so I am then just freespinning with no resistance. A quick click on the shifter and the shift back to the middle ring is flawless, and then to high is flawless.
The other thing that occasionally happens is that when I try to shift from high to the middle ring, the chain will drop all the way to the low gear ring.
Up shifts from any gear are always flawless, the downshifts, not so much.
I have already read two different tutorials (Sheldon Brown's and another one) about adjusting the FD, have not tried to do it yet, just searching for info before I attempt the repair.

Sorry for being so long winded on my first post, but I did not know how to describe the probloem otherwise.

Thanks,

Wayne