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Help Chain slack?

Discussion in 'Maintenance' started by ZDave, Dec 3, 2017.

  1. ZDave

    ZDave Well-Known Member Dirty Wheel Club

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    When adjusting the chain do you measure slack when the chain is at its tightest point and base your measurement there or do you keep turning the rear wheel until the tightest point has passed and base your measurement at that point?
     
  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Generally the service manual will tell you under what conditions the chain slack should be set.

    However, as a general rule of thumb, when the drive sprocket, swingarm, and rear wheel are all aligned in a straight line (ie suspension fully compressed) that will be tightest point for the chain, irrelevant of tight spots in the chain itself.

    I do about 2-3 minor services at work every day which involves cleaning, lubricating and adjusting the chain/sprockets. If the bike has a chain for final drive. Working at a BMW dealer there are a lot of bikes with driveshafts and rear diffs.

    To start with, the bikes are always on their centrestands or on a rear swingarm stand. What I do next is clean the chain and sprockets with kerosone soaked into a rag, and rubbing it along the length of the chain while spinning the rear wheel with your other hand, until you have all the gunk off the outer plates and rollers. After that, I scrub between the plates and rollers with a plastic/nylon brush to get any and all gunk off the o-rings. This process is repeated as needed until the chain is spotless and wiping a rag anywhere on the chain results in no dirt or grease coming off.

    After that, I wipe down the chain with a clean dry rag to get any remaining kerosene off, or just leave it to dry off if it's morning tea time :thumb_ups:

    Then, a light coat of chain grease along the inside for one revolution of the chain, and a light coat along either side of the plates to grease the o-rings. Wipe off any excess from the outside of the chain. A major hate of mine is people using too much chain grease... it just turns into glue, flings off everywhere, sticks to everything, and attracts dirt. Not to mention the unspeakable horror when removing the front sprocket cover.

    The difference after a clean and scrub of the chain is like night and day, smooth as butter. The whole point is to get everything properly clean and lubricated for an accurate measurement of chain slack.

    What I then do is spin the rear wheel and find any tight spots, and measure. I set the slack from the tightest spot in the chain, and always in the middle or towards the upper end of the specification. If you constantly adjust the chain to the tighter side, it will actually stretch more and have to be replaced earlier.

    A good way to tell if the chain is to tight is by rotating the rear wheel slowly, if you can see the chain jumping up and down with slow rotation of the wheel, its too tight. Too slack is when you can visibly see it sagging down, or if the chain touches the swingarm/rubbing strip when checking the slack. And of course, using a ruler to measure the slack against the specification.
     
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  3. ZDave

    ZDave Well-Known Member Dirty Wheel Club

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    Hi Linkin,
    Thanks so much for your reply. That’s fantastic. I appreciate the reply and the level of detail. Awesome
     
  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah i agree with Linkin, check your chain with the rear suspension compressed so that the centre of the front sprocket, swingarm bolt and axle are all lined up, this is where you want the minimum movement, eg 20mm-40mm, so set it to 20mm here.
    I use a strap or rope from the tie rail's down to the swingarm to compress the rear end down and get it all lined up first before making adjustment's, and a laser level when possible

    Also when cleaning and regreasing/oiling the chain, make sure the sprocket's and chain are warm
    eg after a ride so the chain oil soak's in better.
    Spray it on while it's cold and most of that oil/grease will flick off
    I use Rock Oil Chain Lube or Castrol Chain Lube on my bike's, both seem to stick to the chain and not come off easily


    [​IMG]
     
  5. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    I use a ratchet strap to get the points in line and adjust from there.
     

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