Dura Ace 9-speed 7700 brifter repair log

Hi,

I've broken down a right hand dura ace 7700 brifter that shifts up, but requires fiddling to shift down. having cleaned it, and reassembled 3 times, I now realise the problem is exactly the one described here (bottom of the page): https://www.norvil.net/pedal/service/shimanosti/duraace9sti/detail.php

there's a throw away line at the end...

Some folks have asked 'can't I just file the burrs off the cage?'.
Sadly not. The profile is very important to syncronise the motion of
the inner and outer levers, as described above. You have to add metal
first. A TIG with a stainless steel filler rod would be ideal because
stainless work hardens.

Has anyone tried this? the TIG welding bit? I might be able to ask a friend, just seeing if anyone has tried before?

Update: Colleague at work is a dab hand at welding, and put a blob of stainless in the damaged area. now need to file it back to original shape. I'll use this thread as a log of the repair in case it helps anyone.

Tig welder settings from my colleague:
Think it was about 70 amps, modulated with pedal, pulse on, set to about 40hz. Pulse current 65%, pulse time probably 40-50%. It was stainless rod, probably 316.

Also the material did react weird at first, but the second attempt worked.

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My favourite shifters, looks wise, and when they work properly the "thunk" and buttery smooth shift is a joy to behold. GLWF

Overdue update. I did a goodly amount of filing, rebuilding, checking, cursing and taking apart again.

In the end I have a working-ish brifter, in that it works, but all the assembly and dissassembly I did has done some damage to the plastic front cover part, and it all gets a bit wonky when I shift.

I think my main problem was that I trusted someone else to tell me what the problem was (I bought this as faulty). I never mounted it to a bike to test it before starting, so I don't know what my progress really is if any. Essentially it was faulty logic to try and fix what felt like bad shifting without it being mounted on handlebars and connected to a derailleur.

Would I do it again? No. definitely not worth the time and effort. The amount of interesting mechanical learning got very thin on the ground as the job progressed, and the fix relies on access to an expert welder (which I am not).

I've attached some pictures, which don't really explain the work done, but may be a useful reference especially the custom tool I made to take it apart in the first place.

TLDR: probably wasn't broken in the first place, so I just got it back to where it was, plus bonus wear and tear from all the manhandling.

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picture of the misaligned plastic part, it goes back to where it should be easily, but pops back out when shifted.

and better view of the spanner, it is an 8mm

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Should have taken it to The Repair Shop on BBC - that watch repair guy is a genius

Kudos for attempting a repair though.

My comment is somewhat flippant but maybe watch repair people would be best suited to fixing this kind of mechanism. I have a pair in the basement that are still "functional" but there's some sloppiness that doesn't go away with new cabling.

definitely felt like reapiring a clock. the number of times i had to get on my knees to look for a spring...

Interesting. My brifter only has seven clicks now instead of eight. Which part in your assembly ^ would cause this?

is it a flightdeck one?

If you follow the disassembly instructions on this page https://www.norvil.net/pedal/service/shimanosti/duraace9sti/strip.php
I think a problem like that would become obvious in the attached picture. Possibly damage to one of the teeth that hold the shifter in gear, or just crud buildup.

also I wouldn't try any of this without spraying a decent amount of wd40 down the cable hole and give it a couple days to break down crud, that could potentially fix it without dissassembly.

happy to lend my ground down spanner if it helps.

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Having read those instructions... you are a very brave bodger!

It helped thinking that it was broken anyway

oh I just remembered, the heat from the weld is so close to some very accurately toleranced holes and they got deformed. I had to do a bit of reaming out of the holes so they would take the pins again. this was awkward and annoying. another reason this fix is not worth it.

maybe watch repair people would be best suited to fixing this kind of mechanism. I have a pair in the basement

I've called the 5.0 and reported you under the modern-day slavery act.