Chain problem. It somehow loosed up

Discussion in 'Frame Mounted Engines' started by lildeezul, Aug 13, 2008.

  1. lildeezul

    lildeezul Member

    ok, well i just got done putting a 48cc on a diamond back frame for a friend of mine. And on his first start, we was riding normal.. and the dang exhuast baffle bolt ( flat style exhuast not round ended) came off, and the baffle was like hanging out.. well a few minutes later the chain someone loosed up and it had a bunch of slack in it.. and it make a clunking noise as if it was hitting the engine.

    anyways, when we installed the chain is was tight, tight enough to run without a tensioner ( this is wat i did to my moondog and no problems) the chain was tight, and idk how but the chain somehow loosened and got alot of slack in it now that it hits the engine...

    Does anyone have a guess or answer ??


    what i believe is that my back wheel could have possible slid foward and make the chain loose.
    but idk.

    anyone else
     

  2. Your mount could have slid down. Show us some pics of your bike if you can.
     
  3. lildeezul

    lildeezul Member

    hmm. i tried looking i couldnt see a visual difference in the mounts.

    but neways i will get pics asap
    ..


    but to let yall know, the diamond back has no tensioner
     
  4. lildeezul

    lildeezul Member

    ok here are some pictures.

    i think i need to run this tensioner. I just afraid of it ending like my other tension on the moondog, ( in the spokes even after i drilled another hole through the frame)

    but i think ima have to run one.

    the thing is idk why it was tight and then loosened.

    but i do have a idea.

    While i was watching my friend dad put the master link on, he put it on backwards.. is the open part supposed to point towards the engine or rear tire.
    and now i cant find the master link clip.
     

    Attached Files:

    Last edited: Aug 14, 2008
  5. BoltsMissing

    BoltsMissing Active Member

    When you get your chain link sorted, use a tensioner.

    The exhaust modification is, you use those PK screws or self tapping screws, hole size 1/8" drill bit.
    Drill 3 or 4 of those around the bottom edge of the exhaust so it fastens that "cup" looking part in.
    Use some exhuast pipe or heat resistant silicon, there is now a super glue that is like loctite or loctite for hi temperature.
    I used a dab exhaust silicon and it work ok, never came off again.
    There is another type of HT exhaust pipe with a single long screw that holds it all in place to. Seems you got the other as shown on your pics.
     
  6. lildeezul

    lildeezul Member

    i cant find the master link anywhere, becase the clip fell off, is it ok just to break the chain anywhere now ?
     
  7. srdavo

    srdavo Active Member

    no dude...you have to find it or it will just fall apart later.
    should be easy to find...the pins stick out a little more than regular links.

    also....if you think your wheel slipped forward....you"ll need to check that too. make sure your wheel is tight & rolling straight....you might be able to take the chain slack out that way.
     
    Last edited: Aug 14, 2008
  8. lildeezul

    lildeezul Member

    yeah, thats exactly what i was looking for.

    hmmm ill guess ill try looking harder
     
  9. BoltsMissing

    BoltsMissing Active Member

    Just noticed on your pic showing the rear wheel nut, did you have a washer or was the nut just raw up against the frame ?

    Pic shows simlilar set up to yours, with washer and tightened very tight.
    It's a bit tricky tightening these cos it slips, you have to hold the wheel in place with one hand and tighten each side a bit at a time and not let it slip till it grips
     

    Attached Files:

  10. lildeezul

    lildeezul Member

    yeah the washer is on there.

    ALso we had three guys, one wedging the tire so that it wont move, and two tighten the bolts on each side.


    btw, just moved the tire all the way back, and still have the same slack.

    im jsut going to take some links out and then install it.

    im just wondering how and why it became so loose.
    my only idea is that it stretch, but idk it stretch in a 5 min ride
     
  11. duivendyk

    duivendyk Guest

    Chains don't "stretch" ,they can wear at the link pins so that the chain length is increased.Therefore if a chains appears to have stretched,either it has been subject to wear (high chain tensionand/or lack of lubrication or the distance between the sprockets has decreased for some reason.It turns out that the slack (measured sideways) is acutely sensitive to changes in the sprocket distance.In fact the following approximate relationship holds:
    (S squared) = D*d , where "S" is sideways slack, "D" is distance between sprockets and "d" is change in sprocket distance.
    To clarify what all this means,lets take a typical example:
    sprockets 18" a part, or D=18 , change in sprocket spacin 1/16" ,we get S squared = 18/16 or S= 1.06 ",resulting in 16 times as much "slack" as the change in sprocket distance !!.So even a small movement of the rear wheel can produce a lot of slack.This is the worst case, if the distance had changed by another 1/16" the slack would have gone up by only 0.5" instead of having doubled, as one might have been led to expect.
    These computations would appear to elucidate what's been observed.My excuses to the mathphobes.
     
    Last edited by a moderator: Aug 14, 2008
  12. relaxxx

    relaxxx Member

    Did you scratch the frame above the rear mount when installing otherwise it sure looks like it slid down about half an inch or so.
     
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