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  1. #1
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    Lefty 120 PBR help

    Ok, as the title suggests, I've got a 2010 lefty 120 pbr. I was having this issue where the fork doesn't quite feel like it "engages" the damping action for 1/2-1" into the travel. I've had it for two seasons now and it hadn't ever been apart and serviced. I suspected it just needed the seals inspected/replaced and the fork oil changed. So today I spent some time doing all the research on here on how to do that.
    There were a couple threads I found particularly helpful in this research:
    Lefty damper oil change

    http://forums.mtbr.com/cannondale/20...t7886906.html#

    http://maximatgmh.free.fr/Instructio...fty%20DLR2.pdf

    lefty PBR 130 tune?

    So after getting together the necessary tools and cracking the fork open, I inspected the seals and they all seemed ok so I proceeded with the damper oil. After reading the Lefty 130 tune thread, it seemed a 7.5wt oil was in order. When I initially got the lefty and coming from a fox, I thought it was "divey" as well. I've adjusted my riding a bit and just generally hang a little farther back on the bike to compensate. But since I was in there messing around AND what I happened to have on hand was 7.5wt, it seemed perfect. I took everything nice and slow trying to be careful to not break or damage anything I would have to replace. That is what usually happens anyhow. It all went fairly smooth and the fork went back together just fine.
    The problem and help I need is this, it's still exhibiting the same behavior prior to servicing. It's got that first 1/2-1" spot that feels undampened. The lockout also feels a little "softer" than I remember, but I didn't take any of the damping mechanism or wavy washers off.
    Any thoughts on what this things to bring it back?
    Thanks for any input. Well input intentioned to be helpful, somehow my threads always seem to take a turn I never saw coming
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  2. #2
    ballbuster
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    I'm not much help...

    Quote Originally Posted by Buzzaro View Post
    Ok, as the title suggests, I've got a 2010 lefty 120 pbr......
    But my Lefty Max 140 also felt 'Divey' to me when I first got it. That bike previously had a Reba on it.

    *edit* It occurs to me that while I have spacers in there to limit the travel, I don't have anything in there to change the spring compression rate through it's travel. As in, the spring is going to compress like it's expecting to go through 140mm of travel, but I have it limited to 110mm of travel for my 29er.

    I actually kinda liked it once I got used to it. I just figured that's the way Leftys are. I'm not sure I would factor that into any kind of a fault with the fork.

    My Lefty Max is out at Mendon as we speak getting a PBR upgrade. I really need to learn to service my Lefty myself. I did all the service on my Reba, except for the once that I couldn't seem to stop from leaking.
    Last edited by pimpbot; 02-19-2012 at 09:01 AM.

  3. #3
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    Since it's a cartridge and you have the tools to remove it just send it to Mendon for service....it needs some real lovin'....
    Sometimes an o-ring you don't even know is there goes bad, or a proper bleed does the trick.
    Send it in....a real service consists of more than just removing a cap and replacing the oil.....only an experienced person should attempt a full cartridge tear down....
    "Common sense isn't always that common!"
    Custom Prophet and Custom Delta V

  4. #4
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    Quote Originally Posted by cdalemaniac View Post
    Since it's a cartridge and you have the tools to remove it just send it to Mendon for service....it needs some real lovin'....
    Sometimes an o-ring you don't even know is there goes bad, or a proper bleed does the trick.
    Send it in....a real service consists of more than just removing a cap and replacing the oil.....only an experienced person should attempt a full cartridge tear down....
    While I don't disagree that pros know the tricks that us hacks will look right over, I don't want to be without my bike right now. We are having an unseasonably dry winter here in California and the weather and trails have been absolutely perfect. I am hoping to get this taken care of with just a few (more) hours of downtime rather than weeks.
    All out of S**** and down to my last F***
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  5. #5
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    Possible cause

    Ok, I noticed this yesterday but didn't originally think it was the problem. I had already solved the issue in my head and it was the damping oil. I think I refilled and bled the damping oil correctly and the symptoms were still there just as before the oil change. I cracked open the lefty again this morning to have another look and see what I missed or what would look different now that the damper isn't the issue, at least from the perspective that I likely did it correctly. Here is what I found:


    Pic1: the area of concern with what I believe are bottoming bumpers
    Pic2: the entire damper assembly for reference
    Pic3: one of the bottoming bumpers as it should be
    Pic4: showing the bumper cracked and easily compressed by hand

    What I think is causing the soft spot at the top of the travel is the easy compression of one or both of those worn out bumpers. Once those are compressed the fork begins to push on the damper assembly and the feel is normal.
    So if anyone with more experience and knowledge could let me know if I am on the right track or way off and looking in the wrong area could let me know, that would be most helpful to me and possibly other lefty owner/abusers.
    Edit: For some reason the pics aren't in the order I uploaded them but the descriptions are correct.
    Attached Thumbnails Attached Thumbnails Lefty 120 PBR help-img_2236resize.jpg  

    Lefty 120 PBR help-img_2237resize.jpg  

    Lefty 120 PBR help-img_2249resize.jpg  

    Lefty 120 PBR help-img_2250resize.jpg  

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  6. #6
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    Looks like you found problem...makes sense now....luckily those top out bumpers don't cost much.
    "Common sense isn't always that common!"
    Custom Prophet and Custom Delta V

  7. #7
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    Quote Originally Posted by cdalemaniac View Post

    Looks like you found problem...makes sense now....luckily those top out bumpers don't cost much.
    After looking and thinking about it more, I believe those bumpers are actually being uncompressed at the beginning of travel. They were probably damaged that way after repeated bottom outs, which are not uncommon for me. I'm usually somewhere around 250lbs+ geared up and have hit the end of travel pretty hard more than a few times.
    As far as how much they cost, the price is $60. Cannondale seems to only sell them in a kit, KH073 which is the SoloAir kit for the 120. If I do end up getting the kit though, I will get the KH085 which is the kit for the 29er. It's got the same top seal as the 120 kit, but it's got a few extra bits that may come in handy for who knows what someday. The other option I'm looking at, is for the bumpers to be sold by RockShox. It looks like they use the same bumpers in their SoloAir forks, this is unconfirmed at this time and just a suspicion. I'm still doing the research on that part.
    I also found these guys who seem to have a lot of the parts for the leftys. Especially the seal, volume tuning, and wavy washer kits everyone messing with travel and tuning of the PBR/XLR leftys are looking for.

    Tuning and Valving - CannondaleExperts.com
    All out of S**** and down to my last F***
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  8. #8
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    Quote Originally Posted by Buzzaro View Post
    After looking and thinking about it more, I believe those bumpers are actually being uncompressed at the beginning of travel. They were probably damaged that way after repeated bottom outs, which are not uncommon for me.
    Tuning and Valving - CannondaleExperts.com
    Actually...no. That's why they're called "Top out bumpers"....they're being compressed by the preload.....the more air pressure, the more they get compressed....if you bottom out the Lefty the big rubber o-ring right under the top cap takes the impact and is the "Bottom out bumper".
    "Common sense isn't always that common!"
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  9. #9
    All Lefty's, all the time Moderator
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    Telescope rebuild time.
    This is a Pugs not some carbon wannabee pretzel wagon!!

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    www.mendoncyclesmith.com

  10. #10
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    Quote Originally Posted by MendonCycleSmith View Post
    Telescope rebuild time.
    Can you explain some more please? Do you mean my symptoms are indicative of a telescope problem and not the top out bumpers I suspect?
    Thanks
    All out of S**** and down to my last F***
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  11. #11
    All Lefty's, all the time Moderator
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    Quote Originally Posted by Buzzaro View Post
    Can you explain some more please? Do you mean my symptoms are indicative of a telescope problem and not the top out bumpers I suspect?
    Thanks
    Bumpers aren't it. You've ridden it for close to two years, and haven't done it yet. They feel weird after a period of non service. When servicing the damper, one ought to do the telescope too.

    It's like changing the oil on the car, without swapping out the filter while you're at it.

    The damper oil isn't the only thing that experiences breakdown with use....
    This is a Pugs not some carbon wannabee pretzel wagon!!

    - FrostyStruthers



    www.mendoncyclesmith.com

  12. #12
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    Quote Originally Posted by MendonCycleSmith View Post
    Bumpers aren't it. You've ridden it for close to two years, and haven't done it yet. They feel weird after a period of non service. When servicing the damper, one ought to do the telescope too.

    It's like changing the oil on the car, without swapping out the filter while you're at it.

    The damper oil isn't the only thing that experiences breakdown with use....
    Got it. I will do some more research and tear into it after today's ride. I will say that I've been pleasantly surprised with all of this. After rebuilding my Fox that I had previously, I expected this to be quite a bit more complicated. Aside from requiring a couple tools you don't normally have laying around, its been fairly easy and straight forward. The information isn't all in one place and you have to search for it, but it's out there. Now as long as I don't let the need bearings and races fly all over the garage when I get into the telescope...
    All out of S**** and down to my last F***
    I think I strained a pucker muscle

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