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  1. #1
    I got 99 projects BluesDaddy's Avatar
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    Suntour MounTech partial teardown and exploded view

    Working on my '84 Le Tour Luxe (gratuitous beauty shot)



    The MounTech rear derailleur was coated in 30 years of greasy grime so I decided to disassemble the bottom end to clean and lube it.



    I looked at the Disraeli Gears page about this derailleur where they describe it as being overly complicated and prone to failure. Fortunately this example is in good shape, but the wheels weren't rolling smoothly.

    Time to take it apart.



    I took photos so I could get the pieces back together correctly. I've winged before and had bad results, so this time I wasn't taking any chances.


  2. #2
    I got 99 projects BluesDaddy's Avatar
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    I took out the pins that hold the two sprung pivots and let the pivots swing to the slack position, then started taking apart the complicated 3rd pivot/jockey wheel.







    Last edited by BluesDaddy; 09-30-12 at 08:54 PM.

  3. #3
    I got 99 projects BluesDaddy's Avatar
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    The jockey wheel runs on a large, thin steel bushing. The pivot spring end distorted the bushing when the spring was at rest, making the pulley stick, but when the spring is up to tension, the problem goes away.







    All clean "exploded view" of the bottom end. I did not feel brave enough (nor did I have the need) to take apart the parallelogram.


    Last edited by BluesDaddy; 09-30-12 at 08:59 PM.

  4. #4
    Senior Member mobilemail's Avatar
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    If you blow it up, I have a couple more in my parts drawer in the came condition - working well, but the top pulley is kinda rough.

  5. #5
    I got 99 projects BluesDaddy's Avatar
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    There is a piece left over! How does this happen?? The ring is a dust seal or maybe a spacer, but the edge is chewed up so I thought it might do harm than good so I left it out.

    But that little bit... what the heck is that?



    It looks like a broken-off tab or maybe a key. It fell out of my cleaning rag. I'm baffled.

    Here's the front derailleur, BTW:



    Looking forward to getting these back on the Schwinn and trying 'em out!
    Last edited by BluesDaddy; 09-30-12 at 09:09 PM.

  6. #6
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    That piece goes in the split of the top jockey wheel spindle, after you install the spring. I think it is supposed to keep the spring seated. My blue line derailleur had one in it, so I reinstalled it.

    Edit,

    Not the jockey wheel spindle, but the spindle where the cage pivots in relation to the body of the derailleur. You can see in the first picture that the slot is full of metal, that is the top of the tab.

  7. #7
    Senior Member mobilemail's Avatar
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    I really like the Mountech front derailleurs. In my experience, they work better for closely spaced chainrings (aka half-step plus granny setups) than modern derailleurs do.

  8. #8
    I got 99 projects BluesDaddy's Avatar
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    Thanks, poke em.

  9. #9
    Senior Member Captain Blight's Avatar
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    Mobilemail, we are of one mind on this. I went through a lot of front mechs finding out what worked and what didn't; and the Mountech just works, and works well. That it's easy on the eyes is a bonus. First-gen Shimano 105 is great for 40-52 jumps, which I also have; but for 1/2 step with bailout ("Eject! Ejeeect!"), nothing beats Mountech. I've got 7 in my Stategic Reserves.

  10. #10
    Senior Member Captain Blight's Avatar
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    BluesDaddy, thanks for this. I've been reluctant to maintain my Mountech mech, solely based on the D.G. info. I can see, now, thanks to your documentation, that it's within grasp of a mere mortal such as myself.

  11. #11
    Senior Member Chris Chicago's Avatar
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    how does it run now? i noticed mine had a rough jockey wheel a couple years ago but never got it running smooth. did your effort do the trick?

    also, I cant figure out where poke em is saying that part goes in the first pic. any clues?

    thanks

  12. #12
    Senior Member acoffin's Avatar
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    Quote Originally Posted by Chris Chicago View Post
    how does it run now? i noticed mine had a rough jockey wheel a couple years ago but never got it running smooth. did your effort do the trick?

    also, I cant figure out where poke em is saying that part goes in the first pic. any clues?

    thanks
    I'm pretty sure the tab goes in the slot in the end of the top return pivot bolt. I hope those words make sense.

    Anthony

  13. #13
    Senior Member smallpox champ's Avatar
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    There are two tabs for both of the lower pivot bolts, they not only seat the spring but also prevent the slotted bolts from pinching. The flared end should be seated against the spring.

    Servicing the derailleur does help the jockey, but it will become rough again. It is a chronic problem and the Achilles Heel of the Mountech.

  14. #14
    I got 99 projects BluesDaddy's Avatar
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    Captain Blight, I think the key is to remove the stop pins so you can de-tension the two sprung pivots, then you can work on them without having springs go flying. The pin for the upper pivot is obvious; it rests against the body of the derailleur near the mounting bolt. In post #1, the 3rd photo, you can see daylight through the hole where it goes. The other pin looks like a screw into the back of the third pivot. See post #2, 3rd photo.

    I'm not done with the overhaul of the bike yet so I can't say how well it'll work. I'll report back when I've tried it out. This is going on a fair-weather road bike; I hope it will go for a while before it gets contaminated again.

  15. #15
    Senior Member Chris Chicago's Avatar
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    So how did it function after the breakdown?

    i ask bc mine just gave out as far as I can tell. I threw a used shimano Altus on the bike in its place and the gears have never shifted better, so I'm not going to try to fix the mountech most likely

  16. #16
    NT... Big Difference...
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    Quote Originally Posted by Chris Chicago View Post
    So how did it function after the breakdown?

    i ask bc mine just gave out as far as I can tell. I threw a used shimano Altus on the bike in its place and the gears have never shifted better, so I'm not going to try to fix the mountech most likely
    Did you see the The Strangest Thing I Found Today..... Thread?
    @fender1 posted this:



    Quote Originally Posted by fender1 View Post
    Figured I would start a thread for the odd things we come across. Be it on the road, found on bikes or whatever. I'll start. Below is a homebrew solution to fix an old Suntour Mountech derailleur. This came to me on a mid-80's mountain bike I picked up recently. Pretty cool repair.

    [IMG][/IMG]
    *Recipient of the 2006 Time Magazine "Man Of The Year" Award*

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  17. #17
    NT... Big Difference...
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    Quote Originally Posted by mobilemail View Post
    I really like the Mountech front derailleurs. In my experience, they work better for closely spaced chainrings (aka half-step plus granny setups) than modern derailleurs do.
    Quote Originally Posted by Captain Blight View Post
    Mobilemail, we are of one mind on this. I went through a lot of front mechs finding out what worked and what didn't; and the Mountech just works, and works well. That it's easy on the eyes is a bonus. First-gen Shimano 105 is great for 40-52 jumps, which I also have; but for 1/2 step with bailout ("Eject! Ejeeect!"), nothing beats Mountech. I've got 7 in my Stategic Reserves.


    I do realize this is an old thread- but this bears repeating- that Mountech FD is the cat's pyjamaz.

    Not only is the Mountech highly functional, not only is it a nice looking unit that's easy to adjust, it's also even lighter than the Suntour XC Pro derailleurs.

    The big thing wrong with this is that it says "Mountech" on it. And people go away screaming like it's a death fork or Helicomatic.
    *Recipient of the 2006 Time Magazine "Man Of The Year" Award*

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  18. #18
    Senior Member Chris Chicago's Avatar
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    that quarter mod is pretty cool. not sure if it would be worth the effort though. mine never ran great and the spring for the pivot to the right of the quarter (in picture) gave out so the cage just flops back and forth like a pendulum. I got really frustrated trying to get it to work while the mosquito were having me for dinner and my kids were asking their usual 15 questions per minute. which is why the cheapo c10 that replaced it is now my favorite bike part.

    bless you c10
    1392793089.jpg

  19. #19
    Senior Member
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    Quote Originally Posted by mobilemail View Post
    I really like the Mountech front derailleurs. In my experience, they work better for closely spaced chainrings (aka half-step plus granny setups) than modern derailleurs do.
    I like them too for 28/38/48 rings.

  20. #20
    NT... Big Difference...
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    Quote Originally Posted by mrmw View Post
    I like them too for 28/38/48 rings.
    Just looking at your "my bikes" thing- do you/didn't you have a Centurion Pro Tour?
    *Recipient of the 2006 Time Magazine "Man Of The Year" Award*

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  21. #21
    Ride, Wrench, Swap, Race dddd's Avatar
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    Back in the day, I fully rebuilt the Mountech rear derailer that came on my 1984 Stupjumper Sport.
    I concluded that the larger the diameter of a pulley bushing, the higher will be the rotating friction.
    That derailer did go on to survive until I sold the bike some 12 years later, but I never repeated the rebuild and just occasionally shot some motorcycle chain lube at the critical big pulley over the following years.

    All "normal" Suntour derailers, except for the later high-zoot models, had (and have) larger-diameter pulley bushings than most other derailers. I think that this dimension was copied from Simplex. It increases contact area while also imparting frictional forces at a greater radius, thus increasing resistance torque and power.
    The high-zoot models had excellent ball-bearing pulleys that could be bought as an accessory to upgrade any derailer with 5mm or 6mm pulley bolts. Great product!

    As for the C10 Altus, I found this style of part-plastic Shimano derailer to work well enough for racing, though in the end I lost a CX race after leading well into the final lap when mine ejected the pulley cage pivot shaft and cage towards the spokes. Ouch!
    Might have been the rebuild of the "A" pivot that I performed, since the internal circlip may have had a "directional" installation that I perhaps didn't notice.
    These circlips have a sharp side and a rounded-edge side iir.
    So, even though there is a stealthily-hidden access plug that allows one to pull out the circlip and remove the cage pivot assembly, I dis-recommend doing this ever.

    Here's a picture of the bike that I raced on (I took off the rack of course), the front derailer is in fact a Mountech, and works nicely while easily staying clear of the crankarm even when riding in the big ring.
    The rear derailer had not yet exploded when this photo was taken some years ago.


  22. #22
    Senior Member
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    Quote Originally Posted by The Golden Boy View Post
    Just looking at your "my bikes" thing- do you/didn't you have a Centurion Pro Tour?
    I would have responded sooner but I got caught up in one of the timeless wonders of the interwebs which I had to watch in its entirety: https://archive.org/details/WhatsOperaDoc

    Yes, guilty. The '83 Centurion Pro Tour 15 is my daily ride right now (full photographs below in its inaugural post), having elbowed its way ahead of the newly revived '82 Schwinn Super Sport S/P which I rode all spring into early June.

    Centurion Pro Tour 15 and The Hawk
    Last edited by mrmw; 07-13-14 at 05:46 AM.

  23. #23
    Senior Member mobilemail's Avatar
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    Hey, if anybody wants to trade me their mountech front for the mountech rear in my junk box, I'll gladly set you up! I will even include the vintage grime!
    As for replacements, I will confess that just about every modern derailleur that I have used shifts with more ease and precision than the mountech did. You don't find as many that had the incredible capacity though. The Shimano Acera has become my go-to budget replacement for the older derailleurs. Cheap, reasonably attractive, shifts well, decent capacity. I do, however, try to keep it out of my spokes. :-)

  24. #24
    Senior Member Pars's Avatar
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    Quote Originally Posted by BluesDaddy View Post
    There is a piece left over! How does this happen?? The ring is a dust seal or maybe a spacer, but the edge is chewed up so I thought it might do harm than good so I left it out.

    But that little bit... what the heck is that?



    It looks like a broken-off tab or maybe a key. It fell out of my cleaning rag. I'm baffled.
    Both of my Cyclone MKII use these, and one is missing the tab thing. These never show up in the exploded parts diagrams online, must have been a design change on the Cyclone at some point. At any rate, I could use one of these tabs if anyone has one laying around.

    I made one from some scrap metal, but it doesn't tighten up as well as the real deal.

  25. #25
    Senior Member Chris Chicago's Avatar
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    pars, I will be willing to sell you on of those tabs for $10.

    oh, I just noticed you are relatively local so that should save on shipping. pm me your address and I will drop an envelope in the mail

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