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Chain tension adjustment noob question

Discussion in 'Trials' started by ejtv, Mar 31, 2013.

  1. ejtv

    ejtv Per ipsum

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    New to trials. My bike chain tension was set up by dealer before shipping bike to me in December. Since then, been riding regularly 5 hrs a week. Figured it is time to check the chain tension. Beta manual a bit confusing on the issue.

    Can someone post a picture of what the proper tension of chain should be?

    Thank you!
    #1
  2. gybeman

    gybeman Been here awhile

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    I'm too lazy to take a picture but the rubber spring tensioner block should be about 1/2" off the swingarm.
    #2
  3. ejtv

    ejtv Per ipsum

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    The tensioner stays 1/2 inch from the swingarm, in its place, regardless of how lose the chain is. When I tighten the chain, then the tensioner moves more than half-inch. So what you're saying is to tighten the chain until the distance between the tensioner and the swing arm is half an inch and no more? Thank you again.
    #3
  4. Sting32

    Sting32 Trials Evangelist

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    It doesnt have to be a whole half inch, when the bike is at rest (you arent on it) the tensioner needs to be off the swingarm. this keeps tension on the chain when the bike is "in the air" so to speak. as you put weight on the bike the chan usually tightens. if the tensioner is touching the swingarm, then it is obviously not taking up any "slack" in the chain. I try to adjust mine to the 1st "snail cam slot" in which the adjuster comes "off" the swingarm, then call it good, my bike has big notches on the snail cam. But that is also because I check it often too.

    Too tight of chain, will just stretch it, I believe.
    #4
  5. gybeman

    gybeman Been here awhile

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    There should be enough spring in the tensioner to touch the swingarm (if you took the chain off). Like the man said, it takes up the slack so if its off the swingarm 1/2-1" theres enough tension on it when its totally unloaded, and it gets tighter as it compresses.
    #5
  6. Twin-shocker

    Twin-shocker Long timer

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    Sit on the bike, and have a helper adjust the chain so there is about 3/4 inch slack. Then put bike on stand, measure distance from chain tensioner to swinging arm, and adjust to that distance in future.
    #6
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  7. alpineboard

    alpineboard Been here awhile

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    When to adjust chain with snail adjuster. OK, my tensioner is totally at its high point, as far as the mechanism will allow it to go, and the chain is developing a bit of slack/ sag at this point. I adjust the snails one position in tighter direction. Now the top of the chain tensioner plastic block is one finger/thumb thickness , approx. 3/4 inch distance from the bottom of the plastic swing arm guard. The manual states to adjust when the distance is less than 20 mm= 0.79" from the actual swing arm (in picture) and not the plastic swing arm guard. But there is not a picture of where it should be after adjustment is made. I may want to ride it a bit more on the loose side before moving the snails one position. I may also want to re work the tensioner spring and I might gain an 1/8 inch more.
    I do not want to ride it with the chain too tight as that would put stress on the counter shaft of engine when bottoming out the rear suspension, and also pre mature stretch the chain.
    "Sit on the bike, and have a helper adjust the chain so there is about 3/4 inch slack. Then put bike on stand, measure distance from chain tensioner to swinging arm, and adjust to that distance in future"
    3/4" in each direction OR 3/4" total? Slack can be measured when sitting on the bike , but a hard one to measure when fully bottomed out rear suspension. Snail are new to me, as my other bikes had the nut adjust with infinite adjustment. With snail you need to wait until the correct time before moving one complete position. thanks, R having fun starting to climb larger rocks
    #7
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  8. Bronco638

    Bronco638 Nobody Home

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    Lots of different methods have been posted. I use the "rule of thumb" as recommended by my (Sherco) dealer: Adjust the cams, on the rear axle, so that you can fit your thumb between the top of the tensioner and the bottom of the swing arm. For me, that's about 3/4" of an inch. IIRC, the Sherco manual states it should be slightly more than that (1.0" to 1.25").

    I put on a new chain and sprockets over the winter. In the process, I measured the new chain versus the old (2 years of use). They were the same length and the cams were in the same adjustment notches. For my bike, the "rule of thumb" works. YMMV. HTH.
    #8
  9. alpineboard

    alpineboard Been here awhile

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    thanks bronco, yes , some one at an event said use the finger rule, thumb rule, approx. 3/4" , distance can be less, but not greater than., "bottom of swing arm" meaning bottom of the plastic swing arm guard. If and when I remove my rear shock , that would be a good time to see what is going on with max and min chain tension and bottoming out of the rear suspension.
    #9
  10. Hoss Cartright

    Hoss Cartright Been here awhile

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    At the two-day trials this weekend, I immediately spotted an almost 20-year old but like new 1999 GG TX270. It jumped right out at me..
    What also jumped right out at me..... Chain as tight as a drum!

    I spoke to the owner of the bike. Heck of a nice guy, he just got it, is new to trials and said he did not get a "workshop manual" with the bike. He said he didn't have a wrench big enough with him for the axle nuts so we helped out at our paddock, took a few minutes to show him a few general things also..

    This chain being way too tight is a thing I see all the time..

    that is all.
    #10
  11. motobene

    motobene Motoing for 46 years

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    I'm amazed at how tough bikes are and how super-tight chains don't break center cases more often.

    I've had bikes roll past me with not only drum-tight chains but also super squeaky dry... the owner apparently registering nothing on the cringe scale while my neck hairs were standing up and I looked like someone had stuck an electric probe in a sensitive orifice!

    The older I get, the less I care about such things. Is that bad?
    #11
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  12. alpineboard

    alpineboard Been here awhile

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    With the Beta evo, I like to run the chain for a while with a bit of slack on the top, when it gets there, If I do not, and adjust a notch before this slack happens, I believe it is too tight, when adjusted, IMO. Plus this gives the nice free flowing chain, all the time.

    It took me a while to figure this out.
    #12
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  13. fluffdad

    fluffdad Dual Spork Group W

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    Question: Are you adjusting the tension with the bike on the ground (static) or on a stand?


    Thanks
    #13
  14. Hoss Cartright

    Hoss Cartright Been here awhile

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    Typically trials bikes have almost zero static sag so this is somewhat of a moot point. Most likely you will find zero difference between the two methods.
    #14
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  15. Hoss Cartright

    Hoss Cartright Been here awhile

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    I remember some of the trials bikes in the 1980s had notches in the snail-cam adjusters. One notch was too tight, then next notch was too loose, so you ran the more loose adjustment until the chain stretched enough to make it into the next notch on the cams.
    I believe I ran into this on the Fantic 307/309 as they also had a chain that ran very close to the swing-arm as the rear sprocket diameter was smaller, which made the adjustment range tighter as well. And they would also break rear hubs if the chain was too tight so all of this was very critical. Especially the early 1989 versions breaking rear hubs.

    My 1987 MERLIN had the widest swing of the variance and the adjustment was also critical.

    JimMerlin1987.jpg

    DG388Lt.jpg
    #15
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  16. Junglejeff1

    Junglejeff1 Long timer

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    That is a pretty crazy wheel set on the lower pic.
    #16
  17. Brewtus

    Brewtus Buffoonery, Inc.

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    And it looks like someone shot the cylinder head with a shotgun..... :lol3
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  18. Norman Foley

    Norman Foley Devotee of the Husqvarna

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    Lightness is rightness....
    #18
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  19. 2whlrcr

    2whlrcr gooligan

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    Tubeless front rim? I remember the wheels, but not that part.
    #19
  20. Huzband

    Huzband Team Dirt

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    You should have seen the cylinder & head on my Sherpa T after my Dad gave it to the machinist at his work. He worked for NASA. :D

    After that I got a little carried away, as 16 year old boys tend to do. I started drilling everything I could take off the bike. Worked fine right up until I went after the front brake stay. :lol3
    #20