Will mountain bike front derailleur work with Shimano Tourney index shifter? I am having trouble getting my Shimano Deore DX front derailleur to work with a Shimano Tourney index shifter. I would like to know if anyone else has made this setup work and am interested if anyone has had success with a different front derailleur. Also, of course, I am interested in any ideas folks might have, besides getting a second bike -- I am mobile and don't have the room -- and I'm both cheap and not rich. Swapping out parts and tires for various uses has worked for me, at least until now.

Here is my setup: 
1990 Specialized Stumpjumper (basic model), Shimano Deore DX derailleurs are original to the bike. 
It has 3x7 gearing. 11-28 at rear, 26-36-46 in front. The only original gear is the biggest in front, a Shimano SG-X 46. 

For my road bike setup, I have a Shimano Sora Flight Deck index shifter on the right -- for my rear derailleur -- and a Shimano Tourney on the left -- for the front derailleur.

I used to have Sora shifters for both derailleurs, but, alas, the front shifter was broken when a family member mailed my bars to me without enough protective packaging. I bought the Tourney on the fly to make a 60-mile group ride.

Factors to consider in any answers folks might provide:


I was able to make the Sora shifters work with this setup.
The front derailleur is stock and pretty beat up. It has some slop and the cage has taken some hits. I have strengthened the cage in the past, so it's likely not perfectly aligned. In the past, this didn't matter. After writing this up, I'm going to see if I can find a replacement online.
I have confirmed the shifter is for a 3x7 setup by checking its model number.
I know how to adjust derailleurs and even checked in with videos by Calvin Jones of Park Tools to make sure I wasn't missing something.
Basically, the Tourney shifter only has enough travel to give me the bottom and middle gear or the middle and top gear.
Oddly, I can get the front shifting to work on my stand, but not when I give it a road test. My wife helpfully suggested my weight is the factor here ... (190 pounds/86 kg, 6 foot/182cm). 


Thank you in advance for any help you folks can provide.
In case anyone is interested, I got the following suggestion on www.bikeforums.net. The limit screws are not an issue, but I bet flex is. I'm going to check it out.

"Since the front shifter works on the tensioned part of the chain, it does take more force for front shifting. If you have the range on the stand, but isn't getting all gears on the road, then either something is flexing, or the limit screws needs to be backed out some to allow a little more overshoot."

Here is a link to that thread: 
http://www.bikeforums.net/bicycle-mechanics/1118824-shimano-tourney-shifter-work-mountain-bike-derailleur.html#post19798217

Here is an update: 

I ended up swapping out the front derailleur, which made it possible for me to shift to all three front rings. However, it was laggy and unpredictable. That got me to look closer at the bottom bracket. I have a bit of slop there, which is likely the final thing -- I hope -- needed to fix this. Alas, I am now thousands of miles from my bike and won't be reunited with it until mid-October, so trying that will have to wait.

Another up date: my front derailleur now shifts great. I repacked the bottom bracket and eliminated that bit of slop. However, I think the biggest factor was that remounting the front chain ring and crank arm actually moved the front gears closer to my frame. I can tell it ended up closer because my limit screw setting was off. Not by much, mind you, but I didn’t need much. This is an old bike; the pedals are a press fit onto the bottom bracket shaft, essentially a square wedge going into a square, tapered hole,

Anyway, now I’m having trouble with my rear derailleur, but that’s a problem already on the way to being solved.