Shimano Tiagra ST-4700 LH lever intermittent problem

[Brucey]

IIRC the springs on the pawls have at least half a turn of preload on them. If one end has simply come unhooked it isn't always obvious where it needs to be hooked back to; it may even look as if it is working in the other direction. If one end has broken off the spring, it is both less obvious what is going on and of course impossible to effect a cure.

FWIW in a LH shifter the 'upshift pawl' needs to be held clear of the ratchet wheel it normally works on except when it is being used; the reason for this is that it would otherwise foul the ratchet wheel during shifts in the other direction. Part of the mechanism either defeats the spring or allows the pawl to move under spring pressure when the paddle is first moved.

Somewhere I have a ST-4700 set I can take a look at, but I can't lay my hands on it right this moment.

cheers

[LinusR]

Thanks for replies.
Re the tension, yes good point, so last night I re-assembled the gear and FD and tensioned the cable, but no luck, problem still there. I did not try more lubricant though, maybe that's worth a try.

Looking at the part more closely (the pawl that is not returning to position) I cannot see what mechanically it is interlinked with it to move it back. It seems to have full freedom of movement through about 180 deg. So it doesn't look like a lubrication problem.

But I did make a discovery this morning. I was thinking there must be something to move it back, so I had a much closer look under a bright light and made a discovery.

Just off to the right of the pawl, on the same spindle, is a tiny coiled spring, which is pinned at one end to the long lever, but at the other end is LOOSE !! So to your comment , Brucey, that could be the spring that i need to get working again. I've attached a pic, the arrow top right shows where it is attached (you can't actually see the connection but it is there, on the right, to the bottom of the large lever) and bottom left is the free end. Now why would there be a loose spring there? It could be there to return the pawl to position ready for the next move to the large ring.

But there appear to be two issues with that hypothesis. One there does not seem to be an obvious place to connect the loose end of that spring to, and secondly if it was to connect to the pawl direct , the way it is positioned the spring tension would be working the pawl away from were it needs to be, rather than pushing it into position.

So I'm thinking now that maybe there was another part ( that has gone missing, hence the sudden fail) , to which this spring attached, and in combination they moved the pawl. Anyone got any pics of the inside working of an ST-4700. LH that they could share? There is nothing like that level of detail on the Shimano documents I've seen.

Meanwhile I'm looking out on ebay for anyone selling a old ST-4700 for parts - if i had a working lever system I could see if mine was any different. In the meantime happy to hear any other suggestions, especially if anyone knows what that spring in the photo is suppose to do. I'm not ready to admit defeat yet - these levers are almost brand new and mostly been used on an indoor turbo trainer.

Thanks


Inkedspring_LI.jpg

I could be wrong here, but the issue I had was with these two levers not moving freely - see yellow arrows. I had to gently work one of them (can't remember which) back and fore after first squirting with GT85 and then lubing with gear oil, while the lever was attached to the mech and with the bike upside down. Then work the downshift and upshift levers normally. This fixed the problem and the pawls would engage. So find the pivot points and lube. Go gently and be patient.

[kaylang]

Magri66, any luck on finding a solution for your broken 4700 front 2x shifter? I just pulled out my same shifter after storing it for the last 18 months. I tried the first few shifts with tension on derailleur and it shifted with a lot of resistance. After a couple more tries it stopped working all together.

I just disassembled the shifter and I too am having the same issue in that the pawl will not stay down enough to shift into big ring unless you manually seat it.

I am heading into the shop now to dissect another shifter and see exactly what holds the tension on it.

If it's hard to tell, I may just use the method mentioned by Brucey and bend the metal tab against the pawl mechanism.

[Brucey]

if the whole affair has gone stiff/won't latch during storage, it is most likely that

a) the FD itself has started to seize up
b) the cable run is draggy
c) the pawls in the shifter are sticky and need a drop of lube

If you have not done so already, I would suggest that you address these possibilities in that order.

cheers

[kaylang]

Magri66,

I found the spring that got disconnected. I got it hooked back on the pawl and now my shifter is working normally again.

There is a hole where the spring connects near the pawl and the other end of that same spring holds that pawl down. It probably got disconnected and is under the pawl when holding the shifter upside down to view internals. If it is below the pawl, it needs to be pulled to sit on the pawl which'll keep it down.

I can send pictures but have to take apart. Let me know if that'll help.